Contemporary Curtain Wall Architecture

Contemporary Curtain Wall Architecture

Scott Murray

Princeton Architectural Press New York

Contents

7

Introduction

8

Part I: A History of the Curtain Wall as Concept and Construct

10

1: The Chicago Frame and the Dilemma of the Wall

24

2: Visions of a Transparent Future

30

3: The Mid-Twentieth-Century Curtain Wall

48

4: New Directions and New Priorities

64

Part II: Performance and Technique

66

5: Curtain Wall System Design

74

6: Building Envelope As Selective Filter

81

Part III: Case Studies

83

Introduction

86

The New 42nd Street Studios Platt Byard Dovell White New York, New York, United States, 2000

94

Melvin J. and Claire Levine Hall KieranTimberlake Associates Philadelphia, Pennsylvania, United States, 2001

100

One Omotesando Kengo Kuma and Associates Tokyo, Japan, 2003

106

William J. Clinton Presidential Center Polshek Partnership Architects Little Rock, Arkansas, United States, 2004

112

Green-Wood Mausoleum Platt Byard Dovell White Brooklyn, New York, United States, 2004

118

LVMH Osaka Kengo Kuma and Associates Osaka, Japan, 2004

126

Seattle Public Library Office for Metropolitan Architecture and LMN Architects Seattle, Washington, United States, 2004

132

Terrence Donnelly Centre for Cellular and Biomolecular Research architectsAlliance and Behnisch Architekten Toronto, Canada, 2005

140

Torre Agbar Ateliers Jean Nouvel Barcelona, Spain, 2005

148

Torre Cube Estudio Carme Pinós Guadalajara, Mexico, 2005

222

United States Federal Building Morphosis San Francisco, California, United States, 2007

154

Netherlands Institute for Sound and Vison Neutelings Riedijk Architects Hilversum, the Netherlands, 2006

230

Yale Sculpture Building KieranTimberlake Associates New Haven, Connecticut, United States, 2007

162

Skirkanich Hall Tod Williams Billie Tsien Architects Philadelphia, Pennsylvania, United States, 2006

236

The Cathedral of Christ the Light Skidmore, Owings and Merrill Oakland, California, United States, 2008

168

Trutec Building Barkow Leibinger Architekten Seoul, Korea, 2006

244

100 Eleventh Avenue Ateliers Jean Nouvel New York, New York, United States, 2009

176

Biomedical Science Research Building Polshek Partnership Architects Ann Arbor, Michigan, 2006

250

166 Perry Street Asymptote New York, New York, United States, 2009

184

ATLAS Building Rafael Viñoly Architects Wageningen, the Netherlands, 2006

257 259 262

Acknowledgments Bibliography Illustration Credits

190

Blue Tower Bernard Tschumi Architects New York, New York, United States, 2007

198

The Nelson-Atkins Museum of Art Steven Holl Architects Kansas City, Missouri, United States, 2007

206

The New York Times Building Renzo Piano Building Workshop and FXFOWLE Architects New York, New York, United States, 2007

214

Spertus Institute of Jewish Studies Krueck + Sexton Architects Chicago, Illinois, United States, 2007

Published by Princeton Architectural Press 37 East Seventh Street New York, New York 10003 For a free catalog of books, call 1.800.722.6657. Visit our website at www.papress.com. © 2009 Princeton Architectural Press All rights reserved Printed and bound in China 12 11 10 09 4 3 2 1 First edition No part of this book may be used or reproduced in any manner without written permission from the publisher, except in the context of reviews. Every reasonable attempt has been made to identify owners of copyright. Errors or omissions will be corrected in subsequent editions. Editor: Laurie Manfra Design: The Map Office, New York

Library of Congress Cataloging-in-Publication Data Murray, Scott (Scott Charles), 1971– Contemporary curtain wall architecture / Scott Murray. p. cm. ISBN 978-1-56898-797-2 (alk. paper) 1. Architecture, Modern. 2. Curtain walls. I. Title. NA2940.M88 2009 721’.2—dc22 2009007097 Special thanks to: Nettie Aljian, Bree Anne Apperley, Sara Bader, Nicola Bednarek, Janet Behning, Becca Casbon, Carina Cha, Penny (Yuen Pik) Chu, Carolyn Deuschle, Russell Fernandez, Pete Fitzpatrick, Wendy Fuller, Jan Haux, Clare Jacobson, Aileen Kwun, Nancy Eklund Later, Linda Lee, John Myers, Katharine Myers, Lauren Nelson Packard, Dan Simon, Andrew Stepanian, Jennifer Thompson, Paul Wagner, Joseph Weston, and Deb Wood of Princeton Architectural Press —Kevin C. Lippert, publisher The author gratefully acknowledges the generous support of the Graham Foundation for Advanced Studies in the Fine Arts and the College of Fine and Applied Arts at the University of Illinois at Urbana-Champaign.

Introduction

Recent years have seen a growing interest among contemporary architects in the innovative use of the curtain wall, which can be broadly defined as the non-load-bearing building envelope that typically hangs like a curtain from a structural frame. In 2008, a New York Times Magazine article on the proliferation of high-profile buildings with custom architectural enclosure systems declared, “We are living in a golden age…for facades.”1 Indeed, curtain walls are transforming not only the aesthetic experience of cities but also the technical performance of buildings with respect to energy efficiency and occupant comfort. In contemporary practice, the curtain wall presents a microcosm of issues important to architecture: climate-responsiveness and energy use, intelligent utilization of resources, advancements in digital design and fabrication, and the timeless desire to create buildings and spaces that function well and engage the imagination. This book aims to explore the curtain wall as both concept and construct, placing recent work by leading architects into the contexts of past and future developments. The curtain wall remains one of the most enduring concepts of modern architectural theory. From its origins in the late nineteenth century, the non-load-bearing facade has been an influential component of each phase of modernism, driving innovation in response to new challenges. The phenomenon of the curtain wall—like its technological impetus, the frame structure—is ubiquitous and malleable. Through the articulation of materials and parts, it can make a building anonymous or iconic; it can make it an energy hog or an energy generator; and it can profoundly influence how people experience and use architecture, to name just a few of the issues that architects face when addressing the broad implications of material selection, detailing, and fabrication methodology. Developments in contemporary architectural design are best understood within their respective historical and technological contexts. Therefore, this book is organized into three parts, corresponding to history, technology, and contemporary design. “Part I: A History of the Curtain Wall as Concept and Construct” traces key milestones, from initial conceptions to subsequent developments in modern architecture. “Part II: Performance and Technique” discusses the materials and methods currently influencing the design, fabrication, and installation of curtain wall systems. “Part III: Case Studies” provides analyses of twenty-four significant buildings completed since 2000.

1 Arthur Lubow, “Face Value,” New York Times Magazine, June 8, 2008, 48–52.

Essay Title

8

Part I: A History of the Curtain Wall as Concept and Construct

1

2

3

The Chicago Frame and the Dilemma of the Wall

Visions of a Transparent Future

The MidTwentieth Century Curtain Wall

4 New Directions and Priorities

Part I: A History of the Curtain Wall as Concept and Construct

10

1

The Chicago Frame and the Dilemma of the Wall 1.1 Construction of the Reliance Building’s structural frame, August 1894

1.1

The Chicago Frame and the Dilemma of the Wall

1.2

1.2 Leiter Building I, Chicago, Illinois, William LeBaron Jenney, 1879 1.3 Ludington Building, Chicago, Illinois, William LeBaron Jenney, 1891

11

1.3

In his 1956 essay “Chicago Frame,” Colin Rowe characterizes the frame structure as a universal theme of mid-twentieth-century architecture, proposing it to be the “essence of modern architecture.” 1 The late-nineteenthcentury development of the frame structure— using columns and beams of concrete, iron, and steel as a replacement for traditional solid-masonry load-bearing walls—marked a major transformation in architectural design and construction, exerting substantial inluence over the commercial and institutional architecture of cities, particularly Chicago, where, as suggested by the title of Rowe’s essay, architects and clients embraced the new technology early on. From its experimental manifestations in the nineteenth century to its proliferation through the present day, the skeleton-frame structure was signiicant not only for its technical achievements and widespread dissemination but also as a catalyst for new conceptions of architectural form. One of the most inluential ideas derived from the frame structure is the modern curtain wall. [1.1] Historian Carl Condit called the invention of skeleton-frame construction “the most radical transformation in the structural art since the development of the Gothic system of construction in the twelfth century.” 2 The importance of this new technology extended beyond the physical frame; it allowed, perhaps even obligated, architects to reconsider the essential character of the exterior wall. Traditionally responsible for a wide range of aesthetic and technical tasks, the outer walls of a building were directly implicated by innovative structural

methods. Whereas they formerly provided enclosure and structural support, the new frame presented an architectural dilemma. Freed of its load-bearing responsibilities, the exterior became a blank canvas. What should be the character of the new wall? What type of skin should enclose the skeleton structure? Although architects and engineers did not arrive at an immediate solution, the curtain wall eventually emerged as a widely accepted response. After more than a century of development, the frame structure and its corollary, the curtain wall, continue to dominate construction today. From his perspective in the high-modern period of the 1950s, Rowe recognized the importance of Chicago’s late-nineteenthcentury building boom and the advancements made during that period. In fact, he equates the relationship between his contemporaries and the city of Chicago to that of the High Renaissance architects and Florence, Italy. The rebuilding effort in the years following the Great Chicago Fire of 1871, which devastated the central business district, was remarkable. Within twenty years, the downtown Loop area was rapidly redeveloped with taller and taller buildings for which the city’s architects methodically explored radically original methods of construction. This intense effort was driven in part by a population explosion: at the time of its incorporation in 1837, the city had four thousand inhabitants; by 1850, there were thirty thousand; and by 1890, it surpassed one million.3 The city was quickly becoming an epicenter of commerce and culture. As density and land values increased, the economic

Part I: A History of the Curtain Wall as Concept and Construct

12

1.4 Second Studebaker Building, Chicago, Illinois, Solon Spencer Beman, 1896 1.5 Gage Group Buildings, Chicago, Illinois, Holabird and Roche, 1899

1.4

beneits of building taller were obvious. Financial demand converged with the commercial availability of elevators and advancements in structural framing, leading to the emergence of the skyscraper, which in turn had remarkable consequences for the building enclosure. 4 The work of a group of architects active in the 1880s and ’90s—who later became known as the Chicago School—deined this era of experimentation.5 Notable buildings from this group are quite numerous and include William LeBaron Jenney’s Leiter Building I (1879), in which timber girders and loor joists were supported by a grid of cast-iron columns, a common construction method at the time. [1.2] A unique strategy was used at the exterior, however, where instead of a bearing wall, iron columns located just inside the enclosure carried gravity loads at the loor perimeter. These columns were clad in non-load-bearing brick piers, kept consistently narrow to maximize the loor-to-ceiling windows. Also designed by Jenney was the ten-story Home Insurance Company Building (1885), considered by many to be the irst modern skyscraper,6 as well as the Ludington Building (1891), one of the irst all-steel structures. [1.3] Later steel-framed buildings, such as the second Studebaker Building (1896) by Solon Spencer Beman and the Gage Group Buildings (1899) by Holabird and Roche in collaboration with Louis Sullivan, feature enclosures that express the underlying frame structure more directly. [1.4] Beman’s Studebaker Building is dominated by large windows and iron-plate spandrels.

1.5

The three Gage Group Buildings were designed to maximize daylighting for the client’s millinery workers. Sullivan was responsible for the design of the more elaborate facade of the northernmost building, which in its articulation suggests a multistory curtain hanging from the cornice. [1.5] A comparative study of two late-nineteenth-century Chicago ofice buildings— the Monadnock Block (1891) and the Reliance Building (1895)—is useful in understanding the impact of the frame structure and the eventual emergence of the curtain wall. Among the many remarkable aspects of these two very different buildings is the fact that they were both designed by the ofice of Daniel H. Burnham and built within ive years of one another. Considered together, the Monadnock Block and the Reliance Building illustrate an important shift in the concept of structure and skin. A proliic architect and planner, Burnham was also responsible for overseeing the planning and construction of the 1893 World’s Columbian Exposition, and his ofice produced inluential city plans for Chicago, Washington, D.C., and San Francisco. Burnham always worked with a junior partner, and the common perception was that Burnham handled the business side of the irm while his partner directed the design process, with Burnham acting as consultant and critic.7 His irst partner, John Wellborn Root (of the irm Burnham and Root), was the primary designer of the Monadnock Block. Root began work on the Reliance Building, but following his untimely death in 1891, the irm was renamed D. H. Burnham

1.6 Monadnock Block, Chicago, Illinois, Burnham and Root, 1891 1.7 Monadnock Block; typical lower-, middle-, and upper-floor plans 1.8 Monadnock Block

The Chicago Frame and the Dilemma of the Wall

13

1.8

1.6

1.7

and Company and a new design partner, Charles B. Atwood, took responsibility for the inal design. Burnham and Root’s sixteen-story Monadnock Block was, for a brief period, the world’s tallest ofice building. [1.6] Although in some ways unprecedented, particularly in height and in its lack of facade decoration, the building was archaic in terms of its structural technology. At a time when all-steel frame construction was considered the future of the tall building, the Monadnock Block was built using the traditional arrangement of solid load-bearing masonry walls at its exterior, with interior loor loads carried on cast-iron columns and wrought-iron beams. Although Root’s initial scheme called for a steel frame with an ornately decorated facade of multicolored brick and terra-cotta, the architect was directed by his clients, Peter and Shepard Brooks, to abandon ornamental embellishments and revert to a traditional masonry wall structure.8 Load-bearing masonry requires that the wall’s thickness increase in relation to a building’s height. The taller the structure, the thicker the wall required to carry its compressive loads to the ground, which in turn requires a heavier foundation to support the weight of the building. [1.7] This type of construction, as commonly used in Chicago, was considered to have a practical height limit of ten stories. The brick wall of the sixteen-story Monadnock Block is 72 inches (1.8 meters) thick at its base. The width of this massive wall, which reveals itself at its recessed windows, has an undeniably powerful presence that

Part I: A History of the Curtain Wall as Concept and Construct

14

1.9 Reliance Building, Chicago, Illinois, D. H. Burnham and Company, 1895 1.9

evokes permanence and strength, but it also takes up valuable loor space, limits the size of the windows (and therefore the amount of natural light that reaches the interior), and was considerably less eficient than steel framing in terms of labor and time required for construction. [1.8] The weight of such a structure can also lead to problems of settlement. Although the Monadnock Block was designed to accommodate 8 inches (0.2 meters) of settlement, over the years it settled more than 20 inches (0.5 meters).9 For these reasons, it was one of the last tall buildings to be built with solid masonry walls; however, architects did not immediately abandon the aesthetic of the brick wall. The transition to curtain wall construction was a gradual process, with an intervening period in which a great many frame-structure buildings were

built that were, as William Dudley Hunt described, “masonry to the eye but steel or reinforced concrete to the mind.” 10 Built just four blocks away and four years later, the ifteen-story Reliance Building is a striking departure from the Monadnock Block and a radical reinterpretation of the oficebuilding facade. [1.9] Although critics at the time were apparently not enthralled—“It is hardly to be supposed. . . that even the designer will consider it a masterpiece,” Charles Jenkins wrote 11—the building was eventually recognized as a milestone accomplishment of the Chicago School. Writing about the Reliance Building several decades later, Condit claimed, “If any work of structural art in the nineteenth century anticipated the future, it is this one,” adding that “Atwood succeeded in developing almost to its ultimate reinement the modern dematerialized

The Chicago Frame and the Dilemma of the Wall

15

1.10 Reliance Building, wall section, 1895 1.11 Reliance Building, typical floor plan

1.10

1.11

curtain wall.” 12 The facade is characterized by great expanses of glass arranged in the “Chicago window” fashion, with a large central pane of glass lanked by narrow operable windows. The glass is set nearly lush within surrounding thin bands of glazedwhite terra-cotta cladding delicately articulated with Gothic-inspired ornamentation. [1.10] The client, William E. Hale, was determined to have a thoroughly modern building, calling for abundant natural light, the latest elevator technology, full electric service, and a telephone in each ofice.13 It is perhaps dificult to grasp the impact that the Reliance Building must have had on Chicagoans in 1895. With their delicate white framing, the glass walls, alternately transparent or relective depending on the time of day and perspective, would have stood in stark contrast to the neighboring dark brick buildings. The speed of construction must have been startling as well. Working with the engineer Edward C. Shankland, Atwood designed a riveted steel-frame structure, the top ten stories of which were erected in just two weeks, a pace unthinkable with traditional masonry structures. In plan, the steel columns are effectively masked from the exterior, incorporated into corners and projecting bay windows. [1.11] The effect is suggestive of the forthcoming modern curtain wall: a minimal, modular expression of the frame’s grid with an inill of large glass panels. The wall is simultaneously informed and inlected by the structural frame, yet is free of it. In later work, such as the Flatiron Building (1902) in New York City, D. H. Burnham and Company would return primarily to the more conservative Beaux Arts–inluenced style of the World’s Columbian Exposition.14 To modern architects, it would later seem that Burnham and Atwood had essentially turned their backs on the new dialogue between structure and skin that they initiated in the Reliance Building, leaving it to other architects to take up the discussion. Both the Monadnock Block and the Reliance Building were designated Chicago Landmarks in the 1970s, and both are still in use today. The Monadnock Block continues to function as an ofice building, while the Reliance Building, following an extensive restoration in 1999, has been converted to a hotel. In a nod to its designers, the building

Part I: A History of the Curtain Wall as Concept and Construct

16

1.12

1.13

is now known as Hotel Burnham; its groundloor restaurant is the Atwood Cafe. The frame structure had reached an important turning point in Chicago in the late nineteenth century, when the availability of steel (a stronger alternative to iron), among other factors, opened up new possibilities at an unparalleled scale. While the concept of the frame structure was certainly advanced during this period, it was not invented then. An exhaustive history of the evolution of frame structures is beyond the scope of this work, but it is worth a brief digression to note some important precedents to the Chicago frame. Kenneth Frampton has delineated the progression of iron applications over the course of the nineteenth century in Europe and the United States, tracing its use from railroads and bridges to the roofs of market halls and arcades and eventually to the framing of fully glazed conservatories and exhibition halls, such as Joseph Paxton’s Crystal Palace (1851) in London.15 With the rise of industry came new uses for iron. Frampton wrote:

The materials of the railway, cast and wrought iron, gradually became integrated into the general building vocabulary, where they constituted the only available ireproof elements for the multi-story warehouse space required by industrial production.16 Frampton also noted that the standard structural I-beam shape, ubiquitous in frame structures today, irst emerged from the typical railway section. Notable early uses of iron framing include two groundbreaking English mill buildings: the irst in 1792, by William Strutt, in Derby; and the second in 1796, by Charles Woolley Bage, in Shrewsbury. Each employed cast-iron columns carrying segmental brick arches. These were followed by the engineer Thomas Telford’s 1829 warehouses at St Katherine Docks, in London, which were built with iron framing encased in brick, reining the techniques used in earlier buildings, with incremental improvements over previous installations.

1.12 Haughwout Building, New York, New York, partial section, west elevation, and floor plan. John P. Gaynor, 1857 1.13 Haughwout Building, south elevation

The Chicago Frame and the Dilemma of the Wall

17

1.14 Thomas Gantt Building, St. Louis, Missouri, partial section and partial floor plan; architect unknown, 1877 1.15 Thomas Gantt Building

1.14

1.15

Of particular interest in the study of the modern curtain wall is the mid-nineteenthcentury era of cast-iron architecture, typiied by the work of New York designer/ builder James Bogardus, the pioneer of the multistory self-supporting cast-iron facade.17 Bogardus received a patent in 1850 for his construction system of manufactured cast-iron columns and girders bolted together to form a rigid frame, which he employed in commercial projects such as the four-story Laing Stores (1849) and a ivestory building at 254–260 Canal Street (1857), which is one Bogardus’s few surviving buildings. He vigorously marketed the cast-iron facade as an eficient and adaptable system that was quick to erect, relatively inexpensive, and resistant to ire. The Haughwout Building (1857) on Broadway in New York City was designed by the architect John P. Gaynor to resemble a Venetian palazzo, and it illustrates the tendency, which was common at the time, to retain intricate historicist ornament even while deploying a new method of construction. [1.12 + 1.13] Still occupied today, the building was the irst structure to be served by a passenger elevator, installed by Elisha Graves Otis. Another striking cast-iron building, which Sigfried Giedion called one of the inest of this period and a forerunner of the Chicago skyscrapers,18 was the Thomas Gantt Building (1877) in St. Louis, Missouri (dismantled in the 1940s). [1.14 + 1.15] These cast-iron facades, with their clear articulation of large metal-framed windows and their system of modular units prefabricated and bolted together on site, clearly preigure the modern curtain wall. At the turn of the twentieth century, architects continued to explore the frame structure and its dual implications for interior space and exterior expression. In 1897, Frank Lloyd Wright designed the provocative Luxfer Prism Skyscraper, an unbuilt plan for a ten-story steel-framed building with a gridded facade of slightly projecting loor-to-ceiling glass panels.19 In Belgium, the architect Victor Horta worked with iron and steel, developing a vocabulary expressive of the ductile nature of those materials. In his buildings, such as the Maison du Peuple (1899) and L’Innovation Department Store (1903), the grid is clearly expressed on the facade with thin iron elements framing large

Part I: A History of the Curtain Wall as Concept and Construct

1.16

panes of glass, but the frame is also shown to be adaptable, embellished now with the subtle curvatures of the Art Nouveau aesthetic.20 [1.16] It was also around this time that architects began designing frame structures with reinforced concrete on a signiicant scale. In Paris, Auguste Perret’s eight-story Rue Franklin Apartments (1903) used a system of reinforced-concrete construction that had been pioneered and patented by the builder François Hennebique in the 1890s. [1.17] The building was one of the irst concrete buildings to use the structural frame itself (clad in terra-cotta) as the primary exterior expression, inilled almost entirely with glass. Architects eventually began to question the standard coplanar positioning of structure and skin. When the structural frame irst arrived to replace the solid bearing wall, it generally retained the wall’s position

18

1.17

at the outermost surface of the building. With this erosion of the bearing wall, the frame made it possible to open up the facade, allowing for the placement of larger and larger windows between structural members, with the obvious beneits of increased daylight, views, and opportunities for ventilation. The window remained a discrete unit, however big it became, serving as a transparent counterpoint to the opaque grid of structure that framed it. In the irst two decades of the twentieth century, architects began experimenting with the possibility of separating the glass membrane of the window from the structural frame, transposing the glass from individual window to continuous wall. Walter Gropius described this phenomenon, writing that “as a direct result of the growing preponderance of voids over solids, glass is assuming an ever greater structural importance,” with the

1.16 L’Innovation Department Store, Paris, France, Victor Horta, 1903 1.17 Rue Franklin Apartments, Paris, France, Auguste Perret, 1903

The Chicago Frame and the Dilemma of the Wall

19

1.18 Fagus Shoe-Last Factory, Alfeld an der Leine, Germany, Walter Gropius and Adolf Meyer, 1911

1.18

walls becoming “mere screens stretched between the upright columns of this framework to keep out rain, cold, and noise.” 21 The gradual improvement in steel and concrete technologies, Gropius wrote, “naturally leads to a progressively bolder (i.e. wider) opening up of the wall surfaces, which allow rooms to be much better lit.” 22 These concepts are evident in several industrial buildings constructed in Germany just after the turn of the century, perhaps most clearly at the Fagus Shoe-Last Factory (1911), designed by Gropius and Adolf Meyer in Alfeld an der Leine. [1.18] Exposed brickfaced concrete columns are recessed behind the plane of glass, revealing the wall to be a nonstructural “curtain.” Between each column, the curtain wall is articulated as a continuous, three-story-high vertical band passing uninterrupted beyond the edge of each loor slab. The wall, with its organizing grid of slender steel mullions, is divided into clear glass panels and metal spandrels, the latter corresponding to the location of loor slabs. At the corner, the structural column is eliminated altogether, allowing the glass planes to meet at a single corner mullion that is no larger than typical. By comparison, the Fagus Shoe-Last Factory makes the curtain wall at the AEG Turbine Factory in Berlin, built just two years earlier to the design of Peter Behrens (for whom Gropius had worked), seem old-fashioned and inelegant. In the Fagus building, we ind many of the elements that would eventually constitute the vernacular language of the curtain wall:

metal mullions spanning vertically from loor to loor, subdivided into a grid of glass panels, the dimensions of which were determined by available plate-glass sizes, and the integration of opaque spandrel panels where needed to mask the underlying structure. A strategy similar to Gropius’s had been used in the fascinating Margarete Steiff toy factory (1903) in Giengen. Although unconirmed, it is believed that Richard Steiff, the grandson of the company’s founder, produced the design.23 In this instance, the structural steel frame is encased in a doublelayer facade, with a continuous outer skin of glass panels set in iron mullions suspended in front of the structure and extending from ground to roof and from corner to corner, with a second wall of glass on the inner side of the columns. Apparently designed for purely utilitarian purposes—admitting ample daylight to the factory while mitigating the inherent thermal issues of single-pane glass— it stands as one of the earliest continuous glass curtain walls and a remarkable precursor to the modern double-skin facades that would proliferate nearly a century later. In the United States, two early-twentiethcentury commercial buildings were particularly innovative in applying the curtain wall concept at an unprecedented scale. In these buildings, the structural frame is set back entirely behind the plane of a glass-and-metal facade, which is suspended from the structure in a continuous surface. The earlier and more obscure of the two is the Boley Building (1908) in Kansas City, Missouri, designed

Part I: A History of the Curtain Wall as Concept and Construct

20

1.19

by Louis Curtiss. The later and better known is the Hallidie Building (1918) in San Francisco, California, by Willis Polk. Each of these buildings has at various times been identiied as the irst large-scale installation of the pure curtain wall concept. Each was built in the center of its respective city, and, like the Monadnock Block and Reliance Building, they mark an important shift in the development of the modern building envelope. Curtiss’s six-story steel-framed Boley Building is believed to be the irst frame structure to use columns of solid rolled widelange sections rather than built-up members.24 [1.19] The separation of skin and structure is emphatic; a continuous wall of glass and steel is suspended from cantilevered loor slabs, which extend ive feet (1.5 meters) beyond the columns. The curtain wall, primarily large sheets of plate glass set within steel mullions, includes painted steel-plate spandrels and is framed by a cornice and corner bays clad in white-enameled terra-cotta (similar to the cladding of the Reliance Building). Curtiss, who practiced in Kansas City from the early 1890s until his death in 1924, was an eccentric character who regularly communicated with the spirit world and was a fervent believer in the Ouija board.25 He was also an undeniably visionary designer. Though not particularly well received or understood at the time, the Boley Building was, in its structure and cladding, a clear precursor to the modern architecture of later decades. Ten years after its completion, at a time when most building facades were signiicantly less than 50 percent window, Polk’s

1.20

revolutionary Hallidie Building became the irst large-scale urban building to feature an all-glass curtain wall.26 [1.20] An unbroken seven-story wall of clear glass panels (with no opaque spandrels) is suspended 3 feet (0.9 meters) in front of the column line. The glass is ixed within a grid of narrow steel mullions, with the occasional pivoting sash for ventilation. The structural system is a reinforced-concrete frame. At the edge of each loor slab, an upturned perimeter beam supports a thin cantilevered slab, which in turn supports the curtain wall and acts as a irebreak between loors. [1.21] The stark purity of the gridded curtain wall is mediated by several ornate ironwork cornices and ire escapes that loat in front of the glass wall. Polk’s client was the University of California (the building is named for Andrew Hallidie, a former regent of the university and the inventor of the cable car), and the unusual decision to use an all-glass facade was allegedly a response to a tight budget and an accelerated six-month construction schedule.27 A review of the building published in 1918 in Architectural Record pointedly avoids any discussion of aesthetics, focusing instead on the practical beneits of increased daylight and loor space, as compared to traditional masonry walls with recessed windows. The Hallidie Building, this article understates, “possesses more than ordinary interest to architects.” 28 It also uncannily anticipates future developments in modern curtain wall design. Interestingly, there is no indication in Polk’s earlier work of anything similar to the groundbreaking Hallidie Building, which

1.19 Boley Building, Kansas City, Missouri, Louis Curtiss, 1908 1.20 Hallidie Building, San Francisco, California, Willis Polk, 1918

The Chicago Frame and the Dilemma of the Wall

1.21 Hallidie Building, wall section

1.21

21

Frampton considers the “unique triumph of Polk’s career.” 29 As early as 1892, the architect had articulated an appreciation for innovation and a progressive stance regarding historic precedent, writing, “Standards in art are set by the best work of [the] ages, but no age. . . is compelled to take its beauty from preceding epochs. . . . We must neither depreciate nor imitate, but we should understand and originate.” 30 There are also interesting connections between Polk and two other igures discussed above: Burnham and Curtiss. Before moving to San Francisco, Polk worked for a time in Kansas City, where he and Curtiss were both members of the Kansas City Architectural Sketch Club in the late 1880s and thus may have known each other personally. 31 The irst commission of Curtiss’s career had been the design of the Missouri State Building for the 1893 World’s Columbian Exposition. And Polk was also associated with the irm of D. H. Burnham and Company for nearly a decade, which included a stint working in the Chicago ofice from 1902 to 1904, 32 where he surely would have become familiar with the Reliance Building, the Studebaker Building, and other works of the Chicago School. Although there is no conclusive proof, it is interesting to speculate that such connections may have inluenced Polk’s design of the Hallidie Building. Along with the Boley Building, it was listed in the National Register of Historic Places in 1971; both are still in use today, dwarfed by surrounding skyscrapers that are built on the principles they pioneered. At the Bauhaus Building (1926), which Reyner Banham called “the irst really big masterpiece of the modern movement,” 33 the glass curtain wall is given its irst truly modern articulation on a large scale. Designed by Gropius and Meyer, the Bauhaus complex is sited in Dessau, Germany, and includes a ive-story student dormitory wing, a threestory classroom wing, and a three-story workshop block. The facade of each wing gives an indication of the function within: the dormitory has individual punched windows and balconies, the classrooms are marked by larger groupings of strip windows, and the collective loft spaces of the workshop are enclosed by a continuous glass curtain wall that is hung outside of the reinforced-concrete frame structure and spans the full height of

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1.22

the building. Perhaps the most striking element of all is the curtain wall itself, which is technically similar to that of the Hallidie Building but utterly free of any historicist ornament. [1.22] It clearly builds upon the architects’ earlier design for the Fagus ShoeLast Factory while making certain reinements, including the elimination of opaque spandrels and the complete setback of the structure. With its steel mullions, pulleyoperated vents, and repetition of standardized units, the Bauhaus Building curtain wall epitomizes Gropius’s concept of a new architecture, characterized by rationalization, machine production, and a new spatial vision.34 Certainly not without controversy or technical deiciencies (such as condensation on the single-pane glass and insuficient acoustic insulation), the curtain wall looms large as an icon of the modern movement and as an “emblem of the machine age.” 35 In 1945, an air raid on Dessau destroyed

the curtain wall of the workshop building. Though rebuilt to some degree, it remained in various states of disrepair until it was restored to the original design in 1976. In 1996, the entire Bauhaus complex was added to the UNESCO World Heritage List; today it houses the Bauhaus Dessau Foundation, a center for interdisciplinary design research. If the frame structure can be considered a feat of engineering, then the curtain wall was architecture’s response, exploiting the frame’s potential to reconceive the building envelope, thereby transforming not only the face of the modern building but also the experience of space within. The early, incremental development of the curtain wall was infused with a spirit of experimentation and informed by a diverse set of ideas about new construction methodologies, new materials, eficiency, mass production, and, as we will see in the next chapter, the expressive possibilities of glass.

1.22 Bauhaus Building, Dessau, Germany, Walter Gropius and Adolf Meyer, 1926

The Chicago Frame and the Dilemma of the Wall

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Endnotes 1 Colin Rowe, “Chicago Frame,” irst published in Architectural Review, November 1956, 285–89. Reprinted in Colin Rowe, The Mathematics of the Ideal Villa and Other Essays (Cambridge, Mass.: MIT Press, 1976), 285–289. 2 Carl W. Condit, The Chicago School of Architecture: A History of Commercial and Public Building in the Chicago Area, 1875–1925 (Chicago: University of Chicago Press, 1964), 79. 3 Louis H. Sullivan, The Autobiography of an Idea (New York: Dover Publications, 1956), 308; and Kenneth Frampton, Modern Architecture: A Critical History (London: Thames & Hudson, 1992), 21. 4 The irst hydraulic elevator in Chicago was installed in 1870 at the Burley and Company Building on West Lake Street. See Condit, The Chicago School of Architecture, 21. In 1899, the critic Montgomery Schuyler claimed that “the elevator doubled the height of the ofice building and the steel frame doubled it again,” as quoted in Frampton, Modern Architecture, 52. 5 Although originally coined by the architect Thomas Tallmadge in 1908 to signify a group of residential designers that included Frank Lloyd Wright, the term Chicago School has since been expanded to include the commercial architects of the 1880s and 1890s. 6 Sigfried Giedion, Space, Time and Architecture: The Growth of a New Tradition (Cambridge, Mass.: Harvard University Press, 1967), 208. 7 A. N. Rebori, “The Work of Burnham and Root,” Architectural Record, July 1915, 41. 8 Kristen Schaffer, Daniel H. Burnham: Visionary Architect and Planner, ed. Scott J. Tilden (New York: Rizzoli, 2003), 10. 9 Condit, The Chicago School of Architecture, 67. 10 William Dudley Hunt, The Contemporary Curtain Wall (New York: F. W. Dodge Corp., 1958), v. 11 Charles E. Jenkins, “A White Enameled Building,” Architectural Record, January–March 1895, 299. 12 Condit, The Chicago School of Architecture, 111. Similarly, Giedion calls the Reliance Building “an architectonic anticipation of the future” and suggests that it was an inspiration for Mies van der Rohe’s visionary skyscraper projects of the 1920s. See Giedion, Space, Time and Architecture, 388. The so-called dematerialization of the curtain wall is the subject of interesting debate in Joanna Merwood, “The Mechanization of Cladding: The Reliance Building and Narratives of Modern Architecture,” Grey Room (Summer 2001): 52–69. 13 Jay Pridmore, The Reliance Building: A Building Book from the Chicago Architecture Foundation (San Francisco: Pomegranate, 2003), 6. 14 Rowe calls the World’s Columbian Exposition the “debacle which overwhelmed these Chicago architects” and “cut short their development.” See Rowe, “Chicago Frame,” 286. Interestingly, when this essay was reprinted in The Mathematics of the Ideal Villa and Other Essays, Rowe inserted a qualiier that was not present in the original version: the exposition was now an “alleged debacle.” 15 The Crystal Palace, a grand exhibition hall, was essentially an immense iron-framed shed clad on all sides in glass. It is often held to be an inluence on later curtain wall development, although this

is disputed by David Yeomans in “The Origins of the Modern Curtain Wall,” APT Bulletin, 32, no. 1 (2000): 13. 16 Frampton, Modern Architecture, 32. Frampton also quotes Walter Benjamin’s 1930 statement, “The rail was the irst unit of construction, the forerunner of the girder.” 17 Margot Gayle and Carol Gayle, Cast-Iron Architecture in America: The Signiicance of James Bogardus (New York: W. W. Norton, 1998). In the foreword, Philip Johnson cites Bogardus as an inluence on the work of Mies van der Rohe at the Illinois Institute of Technology. 18 Giedion, Space, Time and Architecture, 202. 19 Wright would eventually become more interested in working with the cantilever than the frame. For a discussion of the Luxfer Prism project’s role in Wright’s oeuvre, see Michael Mostoller, “The Towers of Frank Lloyd Wright,” Journal of Architectural Education, 38, no. 2 (Winter 1985): 13–17. 20 The historian William J. R. Curtis calls the facade of the Maison du Peuple “every bit as ‘radical’ as Sullivan’s contemporary skyscraper designs in Chicago,” in Modern Architecture Since 1900 (London: Phaidon Press, 2005), 56. First published in 1982. 21 Walter Gropius, The New Architecture and the Bauhuas (Cambridge, Mass.: MIT Press, 1965), 26–9. 22 Ibid., 26. 23 Christian Schittich, et al., Glass Construction Manual (Basel: Birkhäuser, 1999), 25. 24 Fred T. Comee, “Louis Curtiss of Kansas City,” Progressive Architecture, August 1963, 128–34. 25 Ibid. 26 Keith W. Dills, “The Hallidie Building,” Journal of the Society of Architectural Historians, 30, no. 4 (December 1971): 323–29. 27 Nory Miller, “Down and Dirty in 1917,” Progressive Architecture, November 1981, 108–9. The original color scheme of the building was blue and gold, the colors of the University of California. 28 MacDonald W. Scott, “A Glass-Front Building,” Architectural Record, October 1918, 381. 29 Kenneth Frampton and Yukio Futugawa, Modern Architecture: 1851–1945 (New York: Rizzoli, 1983), 194. 30 Willis Polk, “A Matter of Taste,” Wave, November 12, 1892, 16. As quoted in Richard W. Longstreth, On the Edge of the World: Four Architects in San Francisco at the Turn of the Century (New York: Architectural History Foundation and Cambridge, Mass.: MIT Press, 1983), 93. 31 Donald L. Hoffmann, “Pioneer Caisson Building Foundations: 1890,” Journal of the Society of Architectural Historians, 25, no. 1 (March 1966): 68–71. 32 Longstreth, On the Edge of the World, 299–301. 33 Reyner Banham, Age of the Masters: A Personal View of Modern Architecture (New York: Harper & Row, 1962), 157. 34 Gropius, The New Architecture and the Bauhaus, 19–24. 35 Curtis, Modern Architecture Since 1900, 196.

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2

Visions of a Transparent Future

2.1

Visions of a Transparent Future

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The contribution of the present age is that it is now possible to have an independent wall of glass, a skin of glass around a building; no longer a solid wall with windows. Even though the window might be the dominant part—this window is the wall itself, or in other words, this wall is itself the window. And with this we have come to a turning point. . . it is the disappearance of the outside wall.1

2.1 Maison Domino, perspective drawing, Le Corbusier, 1914

This quote, from Arthur Korn’s 1929 book Glass in Modern Architecture, typiies the profession’s growing fascination with the potential dematerialization of the building envelope made possible by the new structural frame and its corollary, the curtain wall. This interest centered on the concept of transparency and the increased use of glass, which was quickly becoming the primary component of the new building envelope. It is therefore important to examine two developing trajectories of the early twentieth century: theories of glass architecture and technologies of glass production. In the early decades of the twentieth century, one of the envisioned promises of modern architecture was a future in which the concept of transparency—in both its literal and phenomenal manifestations2— would have a liberating effect, leading to new and improved modes of cultural expression. Concepts of transparency and luminosity were often equated with enlightenment and considered a bellwether of modern culture, especially in Europe, where architects such as Bruno Taut, Ludwig Mies van der Rohe, and Walter Gropius, among others, led a design movement based on these ideals, which, for them, represented the future of architecture. Although these architects are rightly considered to be among the fathers of modernism, there is another, lesser-known igure whose work was highly inluential in this period. Paul Scheerbart was a Berlin-based poet and novelist whom the historian Reyner Banham has referred to as one of modernism’s “missing pioneers” 3 due to his importance and relative obscurity. In his book, Glasarchitektur, which was published in Berlin in 1914, Scheerbart describes an imagined future world in which glass becomes the dominant material of architecture. This unusual book is comprised of 111 short chapters—some no more than a sentence long—each addressing a speciic

topic related to glass architecture, from the psychological effects of colored glass to the notion of lighting a space via translucent loors. Perhaps most notable, however, is Scheerbart’s dramatic depiction of an entire world of glass architecture, evident here in a passage that seems to acknowledge the ongoing rise of the frame structure: The face of the earth would be much altered if brick architecture were ousted everywhere by glass architecture. It would be as if the earth were adorned with sparkling jewels and enamels. Such glory is unimaginable. . . . We should then have a paradise on earth, and no need to watch in longing expectation for the paradise in heaven.4 Furthermore, Scheerbart articulated his faith in the possibility that this new glass architecture would impact society on a fundamental level: We live for the most part in closed rooms. These form the environment from which our culture grows. Our culture is to a certain extent the product of our architecture. If we want our culture to rise to a higher level, we are obliged, for better or for worse, to change our architecture. . . . We can only do that by introducing glass architecture, which lets in the light of the sun, the moon, and the stars, not merely through a few windows, but through every possible wall, which will be made entirely of glass—of colored glass. The new environment, which we thus create, must bring us a new culture.5 With his lyrical, effusive rhetoric, Scheerbart found an American counterpart in Frank Lloyd Wright. For Wright, glass represented the potential liberation of interior space, the reintegration of the interior with its exterior setting. A transparent envelope would permit a building to merge organically with the landscape. For its ability to aid in this pursuit, Wright referred to glass as a “super-material,” nothing less than a miracle.6 Echoing Scheerbart, Korn, and Mies, Wright wrote, “Walls themselves because of glass will become windows, and windows as we used to know them as holes in walls will be seen no more.” 7 And like Scheerbart, Wright also wrote of an imagined future world constructed of glass:

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Imagine a city iridescent by day, luminous by night, imperishable! Buildings, shimmering fabrics, woven of rich glass; glass all clear or part opaque and part clear, patterned in color or stamped to harmonize with the metal tracery that is to hold it all together. . . .We have yet to give glass proper architectural recognition.8

input from the engineer Max Du Bois, and it seems to point toward Le Corbusier’s development of the free plan and free facade concepts, while simultaneously referencing the earlier concrete work of his former employer, Auguste Perret, and that of François Hennebique. Although Le Corbusier did not explicitly explore the curtain wall in his earliest deployments of the Domino housing system (opting instead for an inill of solid masonry with strip windows), his famous drawing stands as a clear polemic. It was a provocation to architecture, freeing not only the plan but also the elevation, and calling into question the status of the wall, which could now become almost anything, limited only by the architect’s imagination. A few years later, Mies produced plans for two visionary projects for prototypical glass skyscrapers—a faceted, prismatic design in 1921 and a curvilinear construction in 1922, both sited in Berlin. [2.2 + 2.3] Although unbuilt, both projects were designed to employ frame structures, the irst in steel and the second in reinforced concrete, and both were to be fully encased in all-glass curtain walls. Frampton has written that Mies’s 1921 skyscraper project was a direct response to Scheerbart’s Glasarchitektur.10 Mies himself, writing in Taut’s magazine Fruhlicht in 1922, described the relationship of skin to structure in his skyscraper projects as follows:

An obsession with the idea of novelty was a driving force in the work of some architects and writers, who, like Scheerbart, advocated new ways of thinking about architecture and designing buildings, which, the poet argued, would result in an elevation of culture. He was writing at a time when architects were just beginning to rethink the form, substance, and performance of the building envelope. Although Scheerbart died just one year after publishing Glasarchitektur, his continued inluence can be seen in the work of a number of early modern architects, including three mentioned earlier—Taut, Mies, and Gropius. We have already seen evidence of such an inluence in the design of the Bauhaus Building by Gropius and Meyer; in a 1919 letter to a colleague, Gropius wrote, “You absolutely must read Paul Scheerbarth [sic]. In [his] works you will ind much wisdom and beauty.”9 At the same time that Scheerbart was writing in Berlin, the architect CharlesÉdouard Jeanneret (soon to take the pseudonym Le Corbusier) was developing his 1914 proposal, Maison Domino, represented in an iconic and somewhat abstract perspective drawing showing a two-story structure of reinforced-concrete columns and lat slabs, minus any indication of enclosure. [2.1] At irst glance, it would appear that the “disappearance of the outside wall” that Korn postulated had been fully achieved. But Le Corbusier’s drawing was not a depiction of a inished building; rather, it was an illustration of a proposed system for constructing economical mass-produced housing, which he envisioned as a solution for the coming reconstruction of France after World War I. The project’s title was apparently derived from the words domicile (or domus) and innovation; some have also suggested a double meaning, with the observation that when multiple units were arranged in rows or L-shaped plans, they resembled dominos. The frame structure, with its cantilevered loor slabs, was designed with

Instead of trying to solve new problems with old forms, we should develop the new forms from the very nature of the new problems. We can see the new structural principles most clearly when we use glass in place of the outer walls, which is feasible today since in a skeleton building these outer walls do not actually carry weight. The use of glass imposes new solutions.11 Mies’s projects are remarkable for their startling proposed use of an all-glass curtain wall on such immense scales (twenty and thirty stories, respectively) as well as for their prescience. Though lacking in detail, the suggestion of a fully transparent loorto-loor glass enclosure on tall buildings indicated a new direction for the curtain wall. Mies was not interested in merely a simple or literal transparency; he developed a design process using actual glass models to determine the building form, thereby

2.2 Glass Skyscraper Project, perspective drawing, Mies van der Rohe, 1921 2.3 Glass Skyscraper Project, photograph of model, Mies van der Rohe, 1922

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2.2

2.3

27

working to achieve a desirable play of relections on the facade.12 Even in this early work, he displays knowledge of the full expressive range of glass, from transparency to relectivity and even opacity. The irst image one encounters in Korn’s Glass in Modern Architecture is a photograph of Mies’s skyscraper model, as if to suggest that it was the genesis for all that followed. Although these projects by Mies were never realized— the technology did not yet exist to solve the technical requirements of such a curtain wall—the all-glass skyscraper has been a running theme in every subsequent phase of modern architecture. Several decades later, Mies himself would inally have the opportunity to explore these ideas in built form in his highly inluential towers in Chicago, New York, and elsewhere. Though Scheerbart’s Glasarchitektur remained untranslated until 1972, the relevance and inluence of the book’s ideas should not be underestimated. Nearly seven decades after its initial publication, Banham wrote of Glasarchitektur that “of all the visionary writings of that period, this book has the greatest impact nowadays as the concrete and tangible vision of the future environment of man.” 13 What impressed Banham—and what remains impressive today—is Scheerbart’s attention to not only a poetic vision of glass architecture but also his farsighted concern for technical solutions to glass architecture’s potential inadequacies. This is all the more impressive considering that he was primarily a poet, not an architect or engineer. Many of the practical issues Scheerbart touched on in 1914 continue to be the focus of much research today. For instance, he identiied the importance of the double wall, writing that “since air is one of the worst conductors of heat, all glass architecture needs the double wall.” 14 This is a remarkably insightful idea that illustrates his solid grasp of the technical issues related to glass buildings. It foreshadows the development of double-pane insulating glass in the late 1930s as well as the functional, active double-skin curtain wall systems that were not fully developed until the 1980s and 1990s. Scheerbart explains that the insulating cavity between the two glass walls can be utilized for lighting, writing that “with this type of lighting the whole glass house becomes a big lantern.” 15

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He understood that heating and cooling elements should not be placed in the space between walls, as too much warmth or cold would be lost to the outside atmosphere.16 He also recognized that glass architecture is appropriate only in certain climates, namely, in temperate zones and not in tropical or polar regions.17 He had an intuitive understanding of the importance of factors such as climate, energy, and industrial production for the success of the new glass architecture. At the time, the glass industry did not have many solutions to these problems; there would, however, eventually be a number of new inventions and other developments to address such concerns. In its basic form, glass is a mixture of sand, soda, and limestone, heated until molten (about 2,400°F) and then slowly cooled to a solid.18 Humans have produced it for thousands of years in various forms; with gradual reinements and developments, it has become a nearly ubiquitous material in architecture, industry, and art. The type of glass eventually developed for use as windows in building construction is known as architectural glass (as opposed to art glass, automotive glass, or other forms). Since it is typically required in relatively large, lat sheets of various thicknesses and with speciic strength and optical qualities, it has its own unique manufacturing and processing requirements. Scheerbart’s 1914 treatise urged a revolution in glass architecture shortly after a signiicant transformation had already occurred in the architectural glass industry. In 1904, the process of drawn glass was patented in Belgium; a similar process was patented in the United States the following year. This technique involved drawing a sheet of molten glass from a vat, at a rate of up to 120 feet per hour; the sheet was then passed through a series of rollers until cooled. This ribbon of glass could be continuously produced as long as the raw materials were supplied to the melting furnace. In its mechanization, this technique represented a distinct advantage over existing methods, in which single pieces of lat glass were produced through blowing or casting. The invention of the drawn-glass process represented the irst signiicant innovation in lat-glass production in 250 years, and without it, the transparent dreams of early modernism may never have come to fruition.19

The next major breakthrough was the development of tempered glass in the late 1920s. Still in use today, tempering is a secondary process that improves strength characteristics, regardless of the process by which the glass is produced. Also known as toughened glass, tempered glass is made by heating the sheet in a furnace until it begins to soften, at about 1,200°F, then cooling it quickly by blowing air simultaneously on both sides.20 This process induces compression in the outer surfaces, resulting in improved performance under lateral loading. Tempered glass is characterized by its increased strength and the unique way in which it fractures when broken. It is up to four times stronger than regular, nontempered glass (also called annealed glass), and when broken, it shatters into relatively safe, small pieces with dull edges. The invention of tempered glass provided a more durable and safer product that would further encourage the use of larger expanses of glazing in architecture. The Libbey-Owens-Ford Company was a major producer and innovator among United States manufacturers in the earlyand mid-twentieth century. It was one of the irst companies to develop a prefabricated double-pane insulating glass unit, called Thermopane, which appeared in its catalog in 1940. The product addressed one of the major drawbacks of single-pane windows: their poor insulating value. By creating a sealed airspace between two panes of glass separated by a metal spacer, Thermopane and other similar products, such as Pittsburgh Plate Glass’s Twindow, signiicantly improved the U-value. After further improvements to the materials and methods of spacing and sealing, double- and triple-pane insulating units were in wide use, and their prevalence continues in architecture today. In the 1950s, Sir Alistair Pilkington, working in England, invented a new method of architectural glass production—called the loat process—that still dominates the industry and that fed the rapid growth of glass architecture during the second half of the twentieth century.21 Pilkington melts the raw materials and then “loats” the mixture onto a bed of molten tin, the surface of which is almost perfectly lat—thus forming an almost perfectly even surface on both the tin and air sides of the sheet, free of the distortions and waves

Visions of a Transparent Future

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inherent in earlier manufacturing techniques. After partial cooling (to make the glass somewhat rigid), the continuous strip is transferred onto a conveyor of rollers, where it is gradually cooled and eventually cut into pieces. There is no further polishing or grinding required for either surface—a major improvement over previous production methods. Fully automated loat lines now run constantly, twentyfour hours per day, seven days per week.22 Today, there are more than seventy-ive loat plants operating in the world, producing more than 90 percent of the architectural glass manufactured in the Western world.23 In the buildings and texts of the earlyand mid-twentieth century, the modernist ideal of transparency was, in fact, evident both metaphorically and literally. Coupled with the growing importance of views and natural light (and, to a lesser extent, fresh

Endnotes 1 Arthur Korn, Glass in Modern Architecture (London: Barrie & Rockcliff, 1968), 6. First published in German as Glas im Bau und als Gebrauchsgegenstand in 1929. 2 In their seminal essay on transparency, Colin Rowe and Robert Slutzky make an important distinction between the literal and the phenomenal: “Transparency may be an inherent quality of a substance—as in wire mesh or glass curtain wall, or it may be an inherent quality of organization.” Colin Rowe and Robert Slutzky, “Transparency: Literal and Phenomenal,” Perspecta 8 (1963): 45–54. Reprinted in Rowe, The Mathematics of the Ideal Villa and Other Essays, 159–76. 3 Reyner Banham, “The Glass Paradise,” Architectural Review, February 1959, 89. 4 Paul Scheerbart and Bruno Taut, Glass Architecture and Alpine Architecture, ed. Dennis Sharp, trans. James Palmes and Shirley Palmer (New York: Praeger, 1972), 46. This volume contains English translations of Scheerbart’s Glasarchitektur (1914) and Taut’s Alpine Architektur (1919). All quotations are from Glass Architecture and Alpine Architecture. 5 Scheerbart and Taut, Glass Architecture and Alpine Architecture, 41. 6 Frank Lloyd Wright, The Natural House (New York: Horizon Press, 1954), 51. 7 Ibid., 53. 8 Frank Lloyd Wright, “In the Cause of Architecture,” Architectural Record, July 1928, 11–16. A comparison of Wright and Scheerbart is also made in Frampton, Modern Architecture, 187. 9 As quoted in John Stuart, The Gray Cloth: Paul Scheerbart’s Novel on Glass Architecture, trans. John Stuart (Cambridge, Mass.: MIT Press, 2001), xiii.

air) and periodic advances in available technology, this idea found expression in the rapidly growing use of glass in the building envelope. In a broader sense, the concept of transparency in architecture was further embraced as symbol and catalyst for a new, open society. In retrospect, the relative success of this latter agenda has been widely critiqued, as Annette Fierro wrote, “Prophesies of societal reformation were at best naïve, hopelessly confused between the literal properties of architecture and its associated metaphors.” 24 The magical “disappearance of the outside wall” that Korn described in 1929 certainly captures the spirit of the era but would prove, in reality, to be a myth. Further development and dissemination of the glass curtain wall in the mid-twentieth century would require more—not less—attention to the tectonics of materials and their assembly.

10 Frampton, Modern Architecture,162. See also Banham, “The Glass Paradise,” 89, where he writes that Scheerbart “spoke of America as the country where the destinies of glass architecture would be fulilled, and spoke of the propriety of the ‘Patina of bronze’ as a surface. In other words, he stood closer to the Seagram Building than Mies did in 1914.” 11 Ludwig Mies van der Rohe, Fruhlicht (1922), as translated in Peter Carter, Mies van der Rohe at Work (London: Phaidon Press, 1999), 18. 12 Frampton, Modern Architecture, 162. 13 Reyner Banham, The Architecture of the Well-tempered Environment (Chicago: University of Chicago Press, 1969), 125. 14 Scheerbart and Taut, Glass Architecture and Alpine Architecture, 42. 15 Ibid., 51. 16 Discussion of Le Corbusier’s “neutralizing wall” in Banham, The Architecture of the Welltempered Environment, 156–63. 17 Scheerbart and Taut, Glass Architecture and Alpine Architecture, 42. 18 Joseph Amstock, Handbook of Glass in Construction (New York: McGraw-Hill, 1997), 11. 19 Michael Wigginton, Glass in Architecture (London: Phaidon Press, 1996), 55; and Amstock, Handbook of Glass in Construction, 16. 20 Wigginton, Glass in Architecture, 55. 21 Ibid., 64. 22 Amstock, Handbook of Glass in Construction, 4. 23 Ibid., 52. 24 Annette Fierro, The Glass State: The Technology of the Spectacle, Paris 1981–1998 (Cambridge, Mass.: MIT Press, 2003), 39.

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3

The MidTwentieth-Century Curtain Wall 3.1 United Nations Secretariat, New York, New York, Wallace K. Harrison (director of planning), 1950 3.2 United Nations Secretariat, typical floor plan 3.3 Advertisement describing the Secretariat as the “World’s Largest Window,” originally published in Architectural Forum, 1950 3.4 United Nations Secretariat, typical mullion plan detail 3.5 United Nations Secretariat, wall section

3.1

3.2

The Mid-Twentieth-Century Curtain Wall

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3.4

3.5

3.3

In a 1966 review of Mies van der Rohe’s work, the critic Ada Louise Huxtable called the “glass box,” as derived from Mies’s innovations, “the genuine vernacular of the mid-twentieth century.” 1 Acknowledging its deiciencies in the hands of less-skilled architects, she nevertheless saw this building type as a legitimate and occasionally brilliant response to the needs of modern commercial society in the postwar era. Though overly simplistic, the term glass box came to signify an architecture characterized by simple volumetric forms comprised of frame structures enclosed primarily with glass curtain walls. From the late 1940s through the 1960s, this paradigm was methodically explored in diverse building types, on a wide range of scales and in various cities around the world, but it found its most inluential expression in three ofice buildings constructed in New York City in the 1950s: the United Nations Secretariat, Lever House, and the Seagram Building.2 The thirty-nine-story Secretariat (1950) is the largest and most visible component of the United Nations Headquarters, which also includes the General Assembly (1952), the Conference and Visitors Center (1952), and the Dag Hammarskjöld Library (1961).3 Wallace K. Harrison was the director of planning for the complex, leading an international team of architects that included Le Corbusier and Oscar Niemeyer. [3.1 + 3.2] The Secretariat is sited with its long axis parallel to the East River. The skin of this steel-framed tower establishes a clear dichotomy of solid and void. The two wide elevations—facing roughly east and west—

are composed of glass curtain walls designed to maximize daylight and views, while the narrow north and south elevations, clad entirely in Vermont marble, are windowless. The curtain wall is suspended two feet and nine inches (80 centimeters) beyond the perimeter column line and consists of aluminum mullions on four-foot (1.2 meter) centers, spanning loor to loor, into which are inserted 5,400 double-hung aluminum windows and the same number of glass spandrels. [3.3] Blue-green-tinted, heatabsorbing glass is used throughout; at the spandrels, wired glass is used in front of a low masonry wall that is painted black on its outer surface. [3.4 + 3.5] The inal coniguration of the Secretariat curtain wall was the subject of signiicant debate and controversy. During the design team’s deliberations, Le Corbusier had been adamant that the east and west facades should incorporate a system of exterior brisesoleil to protect the glass from excessive sunlight. He had successfully employed the system in previous projects, two of which are discussed in greater detail below. Before construction began, Le Corbusier felt compelled to take his argument to the chair of the UN Headquarters Advisory Committee, writing in a iery letter: “My strong belief is that it is senseless to build in New York, where the climate is terrible in summer, large areas of glass which are not equipped with a ‘brisesoleil.’ I say this is dangerous, very seriously dangerous.”4 His warnings were not heeded. Harrison and the UN Planning Ofice dismissed the proposal, presenting counterarguments that the exterior sunshades would

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add signiicant cost to the project, present a future maintenance problem, and become a snow and ice hazard in winter. It was also argued that the east-west orientation would not be as onerous as some imagined because the Manhattan grid is actually skewed twentynine degrees from true north. Therefore, they claimed, the west facade would actually face northwest, and the harsh effects of the afternoon sun would be diminished. In the end, an analytical study of various glass types and conigurations—including the construction of a four-story mock-up of the curtain wall— convinced Harrison and his colleagues that blue-green-tinted, heat-absorbing glass would be appropriate, both economically and technically, for the curtain wall.5 Throughout the construction phase and upon completion, the building garnered positive attention from architects as well as the general public. But the critic Lewis Mumford, for one, was unimpressed, calling the Secretariat “not a work of three-dimensional architecture, but a Christmas package wrapped in cellophane.” 6 In a review of the building for the New Yorker, he observed that during its irst summer in operation, workers in the Secretariat found that excessive solar heat gain and glare made it necessary to keep the interior blinds fully drawn most of the day, such that “the result of misorienting the Secretariat and using glass so exuberantly is to create a building that functionally is often windowless on all four sides.”7 Various corrective measures, including applying relective ilm to the glass, were eventually attempted to remedy the solar heat gain.8 Le Corbusier was vindicated. Mumford also pointed out that when viewed from the street, the green-tinted glass walls were rarely transparent, as apparently intended, but often rather dark and relective, essentially acting as enormous mirrors to relect the sky and urban context. Mumford did, however grudgingly, acknowledge the mesmerizing and “incomparable” aesthetic effects of the great glass wall from the exterior: “No building in the city is more responsive to the constant play of light and shadow in the world beyond it; none varies more subtly with the time of day.”9 Though clearly lawed in execution, the Secretariat represented a major step forward in the development of the curtain wall, giving it a forceful presence in a prominent building and helping to usher in

a new era of high-rise glass architecture. In the November 1950 issue of Architectural Forum, the magazine’s editors concluded, “Just as the modern Secretariat had supplied a monumental symbol for the UN, so the UN had, in turn, given modern architecture an aura of respectability, an association with world-wide prestige.” 10 After decades of deferred maintenance, the entire United Nations complex, including the Secretariat curtain wall, is slated for a major $1.9 billion renovation project beginning in 2008.11 It is perhaps understandable that Le Corbusier was so spirited in his advocacy for brise-soleil at the United Nations— he had learned this lesson the hard way. His Cité de Refuge (1933), the Salvation Army’s hostel and rehabilitation center in Paris, featured a multistory, hermetically sealed, southfacing curtain wall of single-pane glass. In the heat of summer, this wall created an intolerable greenhouse effect for the rooms within. Thirteen months after the building opened, local planning authorities demanded that operable windows be installed; eventually, the south facade was retroitted with exterior brise-soleil, in the form of projecting vertical and horizontal ins, to mitigate the solar issues.12 To his credit, Le Corbusier had originally envisioned a much more sophisticated enclosure system for the building. His initial design was for a double-skin curtain wall— an example of his mur neutralisant (neutralizing wall) concept, consisting of two layers of glass separated by an interstitial cavity through which, depending on the season, either cooled or heated air could be circulated, thus creating a buffer zone between interior and exterior environments. This enclosure was to be coupled with an advanced central air-conditioning system (quite new and uncommon in France at the time) to maintain comfortable interior conditions.13 For budgetary reasons, the sealed curtain wall was built with just a single pane of glass and the cooling equipment was eliminated altogether (only heating and ventilation were provided), with terrible results. One of the irst large-scale deployments of Le Corbusier’s brise-soleil concept can be found at the headquarters of the Ministry of Education and Health (1943) in Rio de Janeiro, Brazil. Like the United Nations complex, it was designed by a team of architects, in this case headed by Lucio Costa and Niemeyer.

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3.6 Ministry of Education and Health, Rio de Janeiro, Brazil, south elevation, Lucio Costa and Oscar Niemeyer (directors of planning), 1943 3.7 Ministry of Education and Health, north elevation

3.6

3.7

Le Corbusier served as a kind of senior consultant and mentor to the team. The design is also notable as a large-scale implementation of his “Five Points of a New Architecture.” These included pilotis to raise the mass of the building off the ground, the roof garden, the free plan, the free facade, and the horizontal ribbon window. The ministry building, which has been called the origin of modern architecture in Brazil,14 is an obvious precursor to the Secretariat building. The elongated, rectangular tower contains two broad, transparent facades framed by two solid end walls. On the sunless southern side, the building is enclosed with a curtain wall of loor-to-ceiling glass, incorporating double-hung windows for ventilation. This system is repeated on the sunny northern side but with the addition of exterior brise-soleil featuring deep vertical ins supporting adjustable, horizontal cementpanel louvers. [3.6 + 3.7] This design is intriguing not only for its practical problemsolving but also for its recognition that a building should respond directly and speciically to its local climate and orientation. As the Ministry of Education and Health building shows, the brise-soleil system can be inetuned to a site’s sun angles, maintaining the desired effects of the glass wall while mitigating its inherent problems. Banham calls the brise-soleil system one of Le Corbusier’s “most masterly inventions.” 15 In his later buildings, such as the High Court (1955) in Chandigarh, India, and the Carpenter Center (1964) in Cambridge, Massachusetts, the brise-soleil became the dominant expressive element. Along with his neutralizing doublewall concept, the brise-soleil continues to

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3.8 Lever House, New York, New York, Skidmore, Owings and Merrill, 1952 3.9 Lever House, typical tower floor plan 3.10 Lever House, wall section 3.11 Lever House, typical mullion plan detail (left) and window-washing guide rail (right)

3.8

3.9

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3.11

3.10

capture the architectural imagination, as can be seen in several of the contemporary case studies described later in this book. Soon after United Nations employees moved into the Secretariat, construction workers were putting the inishing touches on Lever House (1952) on Park Avenue in New York City. [3.8 + 3.9] This twenty-one-story steel-framed tower was designed by Gordon Bunshaft of Skidmore, Owings and Merrill (SOM). Lever House was the irm’s irst high-rise ofice building, and it established the irm as a leader in this building type, which it would go on to develop in cities throughout the world. An immediate draw for curious visitors who lined up to tour the building,16 Lever House was also well received by the architectural press, as noted in a 1952 article in Architectural Forum describing it as “ininitely more spirited and digniied than any other commercial ofice building in New York.”17 It is perhaps dificult today to imagine the impact this new type of glass skyscraper would have had at the time, with its characteristic lightness and transparency set against the traditional heavy masonry buildings of Park Avenue. Similar to the Secretariat, the Lever House curtain wall consists of a continuous skin of glass framed in metal, including wire glass spandrels to mask the underlying masonry, as required by building code for ire safety. [3.10] The primary glass type is a single pane of blue-green-tinted, heat-absorbing glass— it was claimed at the time to block 45 percent of the sun’s heat—which is held by steelchannel mullions clad inside and out with sixteen-gauge stainless steel. [3.11]

Transparent vision glass constitutes just over 50 percent of the wall. The Lever House contrasts with the Secretariat in several important ways. The glass in Lever House is ixed in place, without operable windows, relying entirely on air-conditioning for interior comfort (ixed glass reportedly cost 30 percent less than operable windows).18 Lever House is also the irst built example of the curtain wall expressed as an uninterrupted glass membrane, stretching around the tower’s corners to cover all elevations equally. The continuous glazing and narrow loor plate ensured that no desk was more than twenty-ive feet from a window. Although not plagued by solar-heat-gain issues to the same degree as the Secretariat, interior blinds in the building were often drawn to control glare within the ofice spaces. Another unique feature was its innovative windowwashing system: A motor-driven gondola carrying two workmen, who were employed full-time for this purpose, was suspended from a crane that moved on tracks along the perimeter of the roof. 19 The gondola was guided on its vertical ascent and descent by steel rails projecting from and integrated within the mullions, corresponding to the centerlines of the structural columns. This elaborate and necessary system—the irst of its kind—points to the importance of maintaining the clean, smooth surface of glass, not only for a soap company like Lever Brothers but also for modern architecture’s image in general.20 Lever House would soon be accompanied, diagonally across Park Avenue, by the thirty-nine-story Seagram Building (1958),

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3.12 Seagram Building, New York, New York, Mies van der Rohe in collaboration with Philip Johnson and Kahn and Jacobs, 1958 3.13 Seagram Building, typical tower floor plan

designed by Mies van der Rohe in collaboration with Philip Johnson and the irm Kahn and Jacobs.21 [3.12 + 3.13] The steelframed Seagram Building was the irst major ofice building designed by Mies (he was seventy-two years old at the time), and it was the fullest expression to date of the ideas he irst explored in the 1920s. Notable for its pure massing, with no setbacks, and the creation of a public plaza at the street edge, the building brought a new aesthetic to the ofice building type, one that would be taken up with great fervor by architects, including SOM, in the years that followed. In contrast to the blue-green coolness of Lever House, the Seagram Building is characterized by a darker, warmer tone, resulting from a continuous curtain wall of bronzetinted glass with bronze spandrel panels and projecting mullions installed outside of the building structure. [3.14] Unlike Lever House and the Secretariat, the Seagram Building’s curtain wall contains glass panels that extend unbroken from loor to ceiling. The glass is supported by custom-extruded, vertical mullions suspended off the loor slabs by steel angles. These I-shaped mullions provide the structural component of the curtain wall, spanning loor to loor, and are placed on the exterior side of the glass, as opposed to the interior, as was the case at Lever House and the Secretariat. [3.15] As the contemporary Spanish architects Iñaki Ábalos and Juan Herreros have noted, the exterior positioning of the mullion gave the facade some depth and a machinelike appearance but provided no technological advantage.22 In fact, this positioning was problematic in

3.12

3.13

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3.15

3.14 Seagram Building, under construction 3.15 Seagram Building, typical mullion plan detail 3.14 3.16 Seagram Building corner

3.16

that it exposed the mullion to weathering and to thermal expansion and contraction. The Seagram Building’s curtain wall system begins at the ceiling of the lobby, giving the impression of a loating mass while exposing the structural columns at ground level. Mumford found Mies’s curtain wall to be a wholly suitable solution: The faces of the building, instead of being an expression of the structure, are frankly and boldly a mask, designed to give pleasure to the eye and to complement, rather than to reveal, the coarser structure form behind it. This is, after all, a logical treatment of the curtain wall, for the very nature of a curtain is to be detached from the structure, not to support it.23 [3.16] Although the Seagram Building was Mies’s largest curtain wall project to date, it was certainly not his irst. In the years leading up to it, he had completed a series of high-rise residential buildings that clearly illustrate the evolution of his curtain wall design, particularly with respect to the relative positioning of structure and cladding. The earliest of these, built on Chicago’s South Side, was the Promontory Apartments (1949), in which the reinforced-concrete frame is clearly exposed and expressed, with an inill of masonry spandrels and recessed steel-framed windows. [3.17 + 3.18] For the same client, developer Herbert Greenwald, Mies then designed 860–880 Lake Shore Drive (1951) on the North Side. Consisting of two twenty-sixstory towers set at right angles and derived from an earlier design for the Promontory

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3.17 Promontory Apartments, Chicago, Illinois, Mies van der Rohe, 1949 3.18 Promontory Apartments, wall section 3.19 860–880 Lake Shore Drive, Chicago, Illinois, Mies van der Rohe, 1951 3.20 860–880 Lake Shore Drive, wall section

3.17

3.18

3.21 900 Esplanade, Chicago, Illinois, Mies van der Rohe, 1956 3.22 900 Esplanade, wall section 3.23 Seagram Building, wall section, Mies van der Rohe in collaboration with Philip Johnson and Kahn and Jacobs, 1958 3.24 Inland Steel Building, Chicago, Illinois, Skidmore, Owings and Merrill, 1958

3.19

3.20

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3.23

39

3.21

3.24

Apartments, this project is considered a milestone in Mies’s work. It was at this point that he irst developed the vocabulary of skyscraper curtain walls that would occupy much of his remaining career and would inluence countless others. [3.19 + 3.20] The glass is still positioned within the structural frame but is now lush with its outer surface. Black-painted steel plates, in the same plane as the glass, cover the edge beams and columns. The glass is held in place using anodized-aluminum glazing frames, incorporating operable hopper windows, which are in turn supported by projecting mullions of black-painted rolledsteel I-sections. The welded-steel curtain wall frames were fabricated in units, two stories high by 21 feet (6.4 meters) wide, and then hoisted into place.24 One block to the north, Greenwald commissioned another pair of apartment buildings from Mies for 900 Esplanade (1956). In these towers, the curtain wall fully encases the reinforcedconcrete lat-slab structure; the glass plane is set twelve inches beyond the outer surface of the structural column. Mies’s trademark projecting mullions are present but are now formed of extruded aluminum, thus reducing the dichotomy of steel mullion and aluminum glazing frame found in the previous project. [3.21 + 3.22] In contrast to the clear glass at 860–880 Lake Shore Drive, a newly developed gray-tinted, heatabsorbing glass appears to merge with its black aluminum framing, giving the facades an abstract uniformity. Due to the elimination of perimeter beams and ceiling cavities, the spandrel is reduced to a minimal expres-

sion of slab thickness, thereby maximizing the proportion of glass. As Phyllis Lambert writes, “900 Esplanade was the experiment that Mies would elaborate and reine in the Seagram Building, which became the iconic embodiment of the Miesian tall building.” 25 Indeed, the Seagram Building section reveals that the curtain wall is now completely free of the structure, passing uninterrupted outside the edge of the frame. [3.23] The Secretariat, Lever House, and the Seagram Building were soon followed by other high-rise buildings that further explored the curtain wall concept and its relationship to structure. At the Inland Steel Building (1958) in Chicago, SOM adheres to the Miesian strategy of an exterior expression of structure—not only for the curtain wall mullions, but also for the building structure. By relegating elevators and other services to a separate tower and inverting the structural columns to the outside of the curtain wall, they were able to create unobstructed ofice loors. The curtain wall itself incorporates stainless steel for the mullion cladding, spandrel panels, and column covers. [3.24] The Inland Steel Building was the irst fully air-conditioned high-rise in Chicago and the irst to use double-pane insulating glass.26 The Corning Glass Works Building (1959) in New York City was designed by Wallace K. Harrison, the chief architect of the Secretariat, and represents a major advancement in the coniguration of the mullion. [3.25] Rather than an assembly of disparate parts clad in a inish material like stainless steel, the mullions at the Corning building consist solely of extruded-

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3.25

3.26

3.25 Corning Glass Works Building, New York, New York, Wallace K. Harrison, 1959 3.26 Corning Glass Works Building, typical mullion plan details 3.27 Manufacturers Hanover Trust Building, New York, New York, Skidmore, Owings and Merrill, 1954

3.27

aluminum sections shaped to interlock. Neoprene gaskets are used to seal joints. The functions of curtain wall substructure, glazing frame, and inished surface are fully integrated. [3.26] This type of dynamic (or split) mullion is still common today, though more attention is now paid to thermal bridging issues. Low- and mid-rise ofice buildings were also sites for curtain wall experimentation. Notable examples include two New York projects by SOM: the four-story Manufacturers Hanover Trust (MHT) Building (1954) and the eleven-story Pepsi-Cola Building (1960). [3.27] Highly unusual for a bank building at the time, the MHT Building incorporates extensive use of clear glass. It did not suffer from signiicant overheating, however, due to nearly constant shade provided by the taller surrounding buildings.27 The bank’s 1,000-ton safe deposit vault is located just ten feet behind the curtain wall at ground level, fully on display for passersby. The Pepsi-Cola

Building incorporates the largest polished plate-glass panels available at the time— 1/2-inch (1.27-centimeter) thick, measuring 9 by 13 feet (2.7 by 4 meters)—set within a delicate frame of silver-anodized extrudedaluminum mullions. [3.28] The vertical mullions follow the Miesian prototype of projecting I-shaped extrusions, but, in this case, the mullion detail reveals that the glazing channel is “hidden” behind the aluminum I-section and the spandrel plates, resulting in a curtain wall of remarkable transparency and simplicity, and one reduced to its essential elements. [3.29] Another elegant incarnation of the midcentury curtain wall is found at the Jespersen Building (1956) in Copenhagen, Denmark, designed by Arne Jacobsen. [3.30] Due to a requirement for automobile trafic to pass under the building at the ground loor, the building mass is raised on two massive columns at the center, from which each loor is cantilevered 18 feet (5.5 meters) on each side. The curtain wall

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3.28 Pepsi-Cola Building, New York, New York, Skidmore, Owings and Merrill, 1960 3.29 Pepsi-Cola Building, typical mullion plan detail

3.28

3.29

is hung off the slab at each loor. [3.31] Though somewhat technologically crude— the mullions are wood faced with aluminum sheets—the curtain wall achieves the reined impression of a loating wall enhanced by the complete lack of any interior structure visible through the glass.28 Although the commercial building was perhaps the curtain wall’s most visible manifestation, it was not the only type in which the curtain wall found expression at midcentury. A brief look at some of the institutional, educational, and residential buildings that incorporated curtain walls tells a more complete history. Mies himself designed some twenty buildings for teaching, research, and housing on the Chicago campus of the Illinois Institute of Technology (formerly the Armour Institute of Technology), where he had been director since 1938.29 These buildings—ranging from the Minerals and Metals Research Building (1943) to S. R. Crown Hall (1956)—were low-rise frame structures, and they can be seen in retrospect as a workshop where Mies developed his approach to metal and glass that deined his later work. On the Massachusetts Institute of Technology campus in Cambridge, Eero Saarinen designed the Kresge Auditorium (1955), a 1,200-seat concert hall covered by a distinctive thin-shell concrete dome that touches the ground at three points. [3.32] As the dome rises to a height of ifty feet (15 meters), the space below is enclosed by a minimal steel-framed curtain wall with clear glass that allows the lobby space to function symbolically as an extension of the exterior plaza. [3.33] From outside looking in, the curtain wall appears

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3.30 Jespersen Building, Copenhagen, Denmark, Arne Jacobsen, 1956 3.31 Jespersen Building, ground-floor plan, upper-floor plan, and section

3.30

3.31

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3.33

3.32 3.32 + 3.33 Kresge Auditorium, Cambridge, Massachusetts, Eero Saarinen, 1955 3.34 + 3.35 Keokuk Senior High School and Community College, Keokuk, Iowa, Perkins and Will, 1954

3.34

3.35

to hang from the edge of the concrete shell; in reality, thin steel columns support it from behind the glass. A steel-framed curtain wall is also used to great effect at Keokuk Senior High School and Community College (1954) in Keokuk, Iowa, designed by Perkins and Will, a irm long known for innovation in school planning. [3.34 + 3.35] A three-story classroom wing is organized with a wide corridor to the south that connects adjacent classrooms and provides expansive views of an amphitheater outside. The corridor is enclosed entirely by a curtain wall of clear glass in steel mullions, with six-inch-deep projecting exterior steel ins and bottomhinged ventilating sashes dispersed throughout the grid. [3.36 + 3.37] As observed in a 1954 Architectural Forum review, the transparency of the curtain wall makes visible the social activities of the school: “At class changes, the whole facade suddenly becomes a fascinating theater of strolling, conversing, criss-crossing adolescents.” 30 The concept of the curtain wall as an expansion of the window into an enveloping enclosure system was employed even at the scale of the freestanding single-family residence. Three compact and iconic modern houses, all completed within a two-year period, best demonstrate this phenomenon: the Glass House, the Farnsworth House, and the Eames House. In each, a steel frame provides the structure, while non-load-bearing walls of glass and other lightweight materials provide enclosure. These boxy houses appear almost as individual loors of urban skyscrapers, pulled out like dresser drawers and deposited on their idyllic sites. Although

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3.36 Keokuk Senior High School and Community College, section, Keokuk, Iowa, Perkins and Will, 1954 3.37 Keokuk Senior High School and Community College, floor plan

3.36

completed irst, Philip Johnson’s Glass House (1949), in New Canaan, Connecticut, was inspired by Mies’s earlier designs for the Farnsworth House (1951), in Plano, Illinois.31 [3.38 + 3.39] Both feature a rectilinear, free plan with an internal service core and a continuous perimeter wall of large plate-glass panels set within a steel frame. There are subtle differences. The Glass House sits directly on a brick base, while the Farnsworth House is elevated off the ground. In the Glass House, the steel frame is painted black, while Farnsworth’s is white. The glass in the Glass House is set at the exterior face of the columns; at Farnsworth, the columns project, with the glass set at their interior faces. In both cases, though, the overriding characteristic is that of literal transparency, achieved through the dissolution of the traditional wall. The Eames House (1949), in Paciic Palisades, California, illustrates a more eccentric approach in which color, composition, and variation in purpose— rather than literal transparency—are the deining attributes of the facade. Oficially known as Case Study House #8 (commissioned by Arts & Architecture magazine), the building was designed by Charles and Ray Eames to demonstrate an artful and innovative use of industrial technology in response to postwar housing needs. Four-inch (0.1-meter) steel H-columns provide the structural framework (erected in just a day and a half), establishing an organizing module within which a grid of panels is set.32 [3.40] The inill panels vary from painted cementitious panels in a range of colors to transparent, translucent, and wired glass. In addition to a personal aesthetic agenda, the arrangement of

these materials within the facade is inluenced by the function of the spaces within, providing varying degrees of transparency or privacy as appropriate. The Eames House established an enduring example of a curtain wall used not merely as a neutral, consistent grid but as a mutable and responsive system of enclosure. The inluential curtain wall designs of the 1950s, as pioneered by SOM, Mies, and others, were received by the architectural profession and the construction industry as prototypical systems that could be easily manufactured and endlessly repeated (usually with some variation in aesthetic or an occasional innovation in technique). Lever House, Banham wrote, was “an uncontrollable success” that, along with the Seagram Building, would be “imitated to the point of tedium.” 33 Many cities around the world would soon have their own versions of Lever House and the Seagram Building. Along with the curtain wall’s widespread propagation came an inevitable backlash. An article pointedly titled “The Monotonous Curtain Wall” appeared in Architectural Forum in October 1959, offering the following indictment of the status quo in contemporary architecture: The standard curtain wall—perhaps America’s single most important building innovation in the past decade or so—is fast becoming, in the hands of less-thansensitive architects and manufacturers, one of the most irritating eyesores on the U.S. scene.34 Just as Colin Rowe lamented that the frame structure eventually came to represent

3.37

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3.38 Glass House, New Canaan, Connecticut, Philip Johnson, 1949 3.39 Farnsworth House, Plano, Illinois, Mies van der Rohe, 1951

3.38

3.39

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3.40 Eames House, Pacific Palisades, California, Charles and Ray Eames, 1949

3.40

“the nakedly irresponsible agent of a too ruthless commercialism,”35 the gridded glassand-metal curtain wall was soon equated with a menacingly anonymous and ubiquitous corporate culture. This critique of the curtain wall was international in scope and even reached into popular culture. See, for instance, the French director Jacques Tati’s 1967 ilm Play Time, in which the protagonist struggles to ind his way through a future version of Paris composed entirely of monotonous glass skyscrapers, each sporting an identical curtain wall. At one point, a character visits a travel agency and sees posters advertising various destinations around the world—all of them featuring an image of a skyscraper indistinguishable from those

visible just outside the shop window. Architectural critics were generally correct in pointing out that the main problem was the manner in which architects and builders were unimaginatively deploying the curtain wall, not in the idea of the curtain wall itself as a method of construction. Huxtable wrote in 1966, “The ‘glass box’ is the most maligned building idea of our time,” but “It is also one of the best.”36 In the following decades, architects would seem to engage with the prevailing criticism, exploring new vocabularies for the curtain wall beyond the dogma of high modernism and developing new solutions to the inherent, and soon to become highly problematic, environmental inadequacies of the midcentury curtain wall.

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Endnotes 1 Ada Louise Huxtable, “Mies: Lessons from the Master,” Will They Ever Finish Bruckner Boulevard? (New York: Macmillan, 1970), 205. First published in the New York Times, February 6, 1966. 2 These three buildings were preceded by Pietro Belluschi’s Equitable Savings and Loan Association Building (1948), a twelve-story ofice building in Portland, Oregon, clad with a lush skin of glass and aluminum panels. The articulation of the curtain wall, however, retained a strong expression of the structural grid rather than a continuous skin of glass, which is the innovation of later towers. 3 The United Nations was established in 1945. The design process for the UN Headquarters in New York began in 1947. Groundbreaking took place in 1948, and the original complex was completed in 1952. See Robert A. M. Stern, Thomas Mellins, and David Fishman, “United Nations,” New York 1960: Architecture and Urbanism between the Second World War and the Bicentennial (New York: Monacelli, 1995), 601–40. 4 As reported in “The Secretariat: A Campanile, a Cliff of Glass, a Great Debate,” Architectural Forum, November 1950, 108. 5 Stern, Mellins, and Fishman, New York 1960, 613. 6 Lewis Mumford, “Magic with Mirrors,” From the Ground Up: Observations on Contemporary Architecture, Housing, Highway Building, and Civic Design (New York: Harcourt Brace, 1956), 37. The essay was originally published in the New Yorker in 1951. 7 Lewis Mumford, “A Disoriented Symbol,” From the Ground Up, 49. The essay was originally published in the New Yorker in 1951. Mumford also quotes Henry-Russell Hitchcock saying, “The most signiicant inluence of the Secretariat…will, I imagine, be to end the use of glass walls in skyscrapers— certainly in those with western exposures, unless exterior elements are provided to keep the sun off the glass.” 8 See interview with Robert Heintges in “Mr. Glass,” The Architect’s Newspaper, June 20, 2007. 9 Lewis Mumford, “Magic with Mirrors,” From the Ground Up, 40. 10 “The Secretariat: A Campanile, a Cliff of Glass, a Great Debate,” Architectural Forum, November 1950, 112. 11 David D’Arcy, “New Scenery for the World’s Stage,” The Architect’s Newspaper, June 25, 2008. 12 Banham, The Architecture of the Well-tempered Environment, 156–58. 13 Kenneth Frampton, Le Corbusier: Architect and Visionary (London: Thames & Hudson, 2001), 101–3. 14 Elisabetta Andreoli and Adrian Forty, Brazil’s Modern Architecture (New York: Phaidon Press, 2004), 113. 15 Banham, The Architecture of the Well-tempered Environment, 158. 16 Mumford, “House of Glass,” From the Ground Up, 156. 17 “Lever House Complete,” Architectural Forum, June 1952, 104.

18 Jürgen Joedicke, Ofice Buildings (New York: Frederick A. Praeger, 1962), 94. First published in German in 1959. 19 “Lever House, New York: Glass and Steel Walls,” Architectural Record, June 1952, 130–35. 20 Hillary Sample, “Maintenance Architecture,” Praxis, 6 (2004): 106–13. 21 Stern, Mellins, and Fishman, “Seagram Building,” New York 1960, 342–52. 22 Iñaki Ábalos and Juan Herreros, Tower and Ofice: From Modernist Theory to Contemporary Practice (Cambridge, Mass.: MIT Press, 2003), 113. 23 Lewis Mumford, “The Skyline: The Lesson of the Master,” the New Yorker, September 13, 1958, 143. 24 Carter, Mies van der Rohe at Work, 46. 25 Phyllis Lambert, ed., Mies in America (New York: H.N. Abrams, 2001), 374. Lambert herself was instrumental in convincing her father, Samuel Bronfman, the president of Seagram and Company, to hire Mies for the Seagram Building. 26 Lawrence Okrent, “Inland Steel Building,” AIA Guide to Chicago (Orlando, Fla.: Harcourt, 2004), 67. 27 Stern, Mellins, and Fishman, “Seagram Building,” New York 1960, 374. 28 Joedicke, Ofice Buildings, 192–93. 29 Jean-Louis Cohen, Mies van der Rohe (Basel: Birkhäuser, 2007), 104–9. First published in 1994. 30 “Sprawling Campus-Type High School Contradicts Dogma,” Architectural Forum, October 1954, 112–19. 31 Frampton, Modern Architecture, 240. 32 Gloria Koenig, Charles & Ray Eames (Cologne: Taschen, 2005), 32–9. 33 Banham, Age of the Masters, 114–15. 34 “The Monotonous Curtain Wall,” Architectural Forum, October 1959, 142–47. 35 Rowe, “Chicago Frame,” as reprinted in The Mathematics of the Ideal Villa, 108. 36 Huxtable, Will They Ever Finish Bruckner Boulevard?, 205.

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4

New Directions and New Priorities

4.1

New Directions and New Priorities

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4.2

4.1 + 4.2 Deere and Company Headquarters, Moline, Illinois, Eero Saarinen and Associates, 1964 4.3 Partial wall section

4.3

Beginning in the 1960s and continuing to the present day, the approach to the curtain wall has been characterized by diverse strategies, due in part to the vicissitudes of architectural fashion at large and to the growing impact of global environmental and economic forces. It seems that each new decade has brought with it a new design doctrine—postmodernism, hightech, deconstructivism, critical regionalism, green architecture—and the curtain wall concept has been transformed in response. Energy crises in the 1970s and again in the early twenty-irst century, as well as the rise of an environmentalist sensibility, have resulted in widespread and ongoing reevaluation of architecture in general and a refocusing on the performance of the building envelope. The curtain wall’s endurance through this turbulent period demonstrates that it is indeed a mutable concept, capable of adapting to nearly any design strategy, from minimalist transparency to the historicist nostalgia of postmodernism. A study of several buildings from this period will illustrate how the curtain wall has adapted to various stylistic impulses while also incorporating incremental advances in technology. At the John Deere & Company Headquarters (1964) in Moline, Illinois, Eero Saarinen and Associates designed a curtain wall that seamlessly melded the Miesian vocabulary of glass and steel with Le Corbusier’s brise-soleil concept, resulting in a strikingly unique and inluential building. [4.1] This complex of three linked buildings—a seven-story administration building, a public exhibition and

auditorium building, and an engineering wing—is nestled into its wooded suburban site, only occasionally emerging into view from the dense surrounding foliage. The exterior of the building is characterized by an external structural skeleton of widelange steel members and a system of steel brise-soleil that project forward from a backdrop of gold-tinted relective glass. Saarinen found inspiration in the iron and steel farm machinery manufactured by the John Deere Company, and he translated this inluence into a critique of what he called the “slick, precise, glittering” glass box: Having decided to use steel, we wanted to make a building that was really a steel building (most so-called steel buildings seem to me to be more glass buildings than steel buildings, really not one thing or the other). We sought for an appropriate material—economical, maintenance free, bold in character, dark in color.1 For the steel, Saarinen speciied an alloy known as weathering steel (and by the trade name Cor-ten) that resists corrosion by forming a continuous outer coating of iron oxide to protect the steel within. The material thus naturally develops a dark reddish-brown color tone and does not require painting. Saarinen was the irst to use weathering steel, originally used in railroad and bridge construction, in an architectural application. He described the impetus of the curtain wall design as: Having selected a site because of the beauty of nature, we were anxious to take

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4.4 College Life Insurance Building, Indianapolis, Indiana, Roche and John Dinkeloo, 1971

4.4

full advantage of views from ofices. To avoid curtains or Venetian blinds, which would obscure the views, we worked out a system of sun shading with metal louvers and also speciied relective glass to prevent glare.2 [4.2] The gold-tinted relective-coated glass, a relatively new product at the time, reportedly rejected up to 70 percent of heat striking the surface.3 Though mirrorlike by day, relecting the adjacent steel sunshades and tree branches, this glass is fully transparent from the interior; at night, with interior lighting, the glass becomes transparent from the exterior as well. The laminated glass is supported by vertical wide-lange steel mullions, to which it is attached through the use of continuous neoprene glazing gaskets. Together, the relective coating and brise-soleil provide effective protection against solar heat gain and glare at the loor-to-ceiling glass walls. [4.3] Concurrently with the Deere Headquarters, Saarinen’s ofice was planning two other major corporate commissions: IBM’s Thomas J. Watson Research Center (1961) in Yorktown Heights, New York, and Bell Laboratories (1962) in Holmdel, New Jersey. Both are immense, pristine volumes clad primarily in glass. Notable for their sheer size—IBM has a curving gray glass wall measuring 1,000 feet (300 meters) long and Bell Labs is a ive-story relective glass box totaling 700 feet (210 meters) in length— these buildings lack the site speciicity and intelligent solar-control strategies of the Deere Headquarters. Although Saarinen died in 1961 at the age of ifty-one, before

the completion of many of his largest commissions, his posthumous inluence was evident in the work of architects who emerged from his ofice to form their own practices, including Kevin Roche (who oversaw completion of the Deere complex in Saarinen’s absence), Gunnar Birkerts, and Cesar Pelli. The multilayered metal-and-glass curtain wall of the Deere Headquarters has likewise been an enduring inluence on architects, as is apparent in several of the contemporary case studies featured later in this book. Following in the footsteps of pioneering work by Saarinen and others, relective coated glass came into widespread use in curtain walls in the late 1960s and into the 1970s, though not often treated with the sensitivity that Saarinen’s buildings displayed. An interesting example is the College Life Insurance Company Building (1971) in Indianapolis, Indiana, designed by Roche and John Dinkeloo. The building consists of three linked pyramidal volumes, each eleven stories tall. [4.4] The towers are organized with service cores in an L-shape along two perimeter concrete walls and open ofice space enclosed by two sloping, relectiveglass curtain walls suspended from concrete loor slabs. This plan establishes a strong duality of opacity and relectivity, with the opaque core walls facing the nearby highway and the relective glass walls opening out toward the landscaped site. The simple yet unusual massing, combined with the relectivity of the glass surface, lends the building an overriding abstract quality, which would come to deine a new trend: the reincarnation of the glass box as a mirrored sculptural

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4.5 + 4.6 John Hancock Tower, Boston, Massachusetts, I. M. Pei and Partners, 1976

4.5

4.6

object. Though originally well received by the press, the structure was not without its technical problems. Soon after the building was occupied, the curtain wall mullions were found to be inadequate to resist wind loads; problems of leakage and glass breakage occurred in about half of the building’s 4,000 insulating glass units, eventually requiring complete replacement of the curtain wall.4 Another, much larger example of the shift toward the abstract, scaleless curtain wall is found at the sixty-story John Hancock Tower (1976) in Boston, Massachusetts, primarily designed by Henry N. Cobb of I. M. Pei and Partners. [4.5] The tower is a surreal variation on the midcentury glass box, with two-way transparency exchanged for one-way relectivity and the pure rectangular plan warped into a rhomboid shape. The curtain wall consists of more than 10,000 large panels of relective coated glass (originally insulating glass, but later replaced with monolithic glass) supported in a grid of extruded-aluminum mullions. The glass panels, measuring about 4.5 by 11.5 feet (1.4 by 3.5 meters), extend continuously from loor to loor with no spandrels (a condition made possible by the inclusion of sprinklers and other life-safety measures).5 [4.6] The Miesian I-shaped mullion is still present, but rather than projecting outward from the glass surface, it is subsumed into the wall, in service to the ideal of a totally lush surface. The John Hancock Tower was controversial in nearly every respect, from its siting on the edge of historic Copley Square to its height and facade treatment. Perhaps its greatest controversy involved a famous

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4.7 + 4.8 Willis Faber and Dumas Building, Ipswich, England, Foster + Partners, 1975

4.7

4.8

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4.9

4.10

4.9 Allied Bank Tower, Dallas, Texas, I. M. Pei and Partners, 1986

glass failure: during a strong storm in January 1973, with the building nearing completion, dozens of glass lites broke and fell down along the west facade, further damaging hundreds of additional lites. The origin of the failure was determined to be related to stresses caused by thermal expansion of the large insulating glass panels, and eventually all of the glass was replaced with new monolithic tempered lites.6 In a thorough review of the newly completed building and its complicated history of glass breakage, critic William Marlin appreciated the tower’s “clean, crisp surfaces” despite its technical troubles, observing that “when the play of light and clouds is right, the building verges on the ethereal, almost disappearing.” 7 To many other critics, however, the 1970s mirror-glass ofice building, typiied by the John Hancock Tower, was “as forbidding, anti-social, and hostile as a person wearing mirror sunglasses.” 8 Norman Foster achieved a major advancement in the quest for a continuous glass skin—a modernist holy grail since Mies’s 1921 project—in his design of the Willis Faber and Dumas Headquarters (1975) in Ipswich, England. [4.7] Amorphous in plan but following the shape of the site, the three-story ofice building is enclosed in a continuous wall of glass; remarkably, it utilizes no metal mullions for support. Recognizing the inherent tensile strength of glass, the entire curtain wall is hung from a rail along the roof of the building, with each piece of glass bolted to the one above with stainless-steel patch plates. For lateral stability, monolithic glass ins are hung from the underside of each cantilevered loor slab. [4.8] With no mullions or

4.10 Mullion plan details at spandrel glass (left) and vision glass (right)

glazing frames, the glass-to-glass joint is minimized to the width of a silicone seal. At the sidewalk, the glass disappears into a slot in the pavement, a further testament to the rigor of the all-glass design. The halfinch-thick tempered glass is bronze-tinted and relective, resulting in a stark contrast between its daytime and nighttime appearance, while the overall design strikes a balance between abstraction and technological showboating. Although not practical for tall buildings, Foster’s suspended glass-in wall has since been used extensively in smaller-scale buildings and discrete spaces such as lobbies and storefronts, and it has been adapted for use with insulating glass and various other structural backup systems, such as cable trusses and nets. Structural silicone glazing was another technology that became important in the drive to minimize framing while maximizing glass surface area. The concept of using silicone sealant as a means of ixing glass to its supporting mullion—essentially gluing the glass onto its frame with no other mechanical means of attachment—had irst been proposed in the 1960s. After extensive testing and small-scale applications, structural silicone came into mainstream use in the United States in the 1980s. The prismatic Allied Bank Tower (1986) in Dallas, Texas, designed by I. M. Pei and Partners, was at the time of its completion the tallest structural siliconeglazed curtain wall in the world, with more than 450,000 square feet (42,000 square meters) of surface area.9 [4.9 + 4.10] This ifty-nine-story steel-framed tower is clad entirely in relective green-tinted glass that

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is structurally glazed, on all four sides, to frames of anodized extruded aluminum. The curtain wall units were assembled in a factory to ensure the essential precision and quality control required for structural silicone application. Prior to installation, a mock-up of the curtain wall was tested for resistance to wind pressure and rain, and once installed, the curtain wall units were tested on site to conirm adequate performance.10 These procedures relect a growing understanding of the science of the curtain wall as well as increased expectations for performance. Testing of custom curtain walls, both in mock-ups and in the ield, is standard practice today. As the modern curtain wall veered in the direction of relective abstraction, some architects began to experiment with an alternative design vocabulary to challenge the dominance of modernism. Though its precise deinition has been much debated, the term postmodernism emerged to describe a new movement that reached its pinnacle of inluence in the 1980s. As journalist and historian William Curtis described the phenomenon in 1984, “The mission is to save the American city from an excess of industrial standardization and the abstract glass box. The prognosis is in the use of metaphors and historical associations.” 11 Philip Johnson’s AT&T Building (1984), in New York City, is emblematic of the values and priorities of postmodernism: a rebuke of modernist dogma in favor of overt historicism, vernacular references, a jokey demeanor, and pop iconography. Johnson, who had worked with Mies on the design of the Seagram Building twenty-ive years earlier, reconceived the commercial skyscraper as a stone monument with a pedimented crown, the glass reduced to relatively small windows punched into massive opaque walls. Although projecting a traditional masonry aesthetic, the thirty-six-story AT&T Building still relies on a steel frame structure; the stone cladding is merely a nonstructural skin—a curtain wall. Granite panels, varying from two to ive inches thick, are individually anchored to a back-up structure of vertical steel tubes spanning from loor to loor.12 In this way, even as the purity of the “glass box” aesthetic lost favor, architects found the curtain wall to be a neutral technology, adaptable to wide array of design ideologies, even those with short life spans. Around the same time that postmodernism was making its impact on architectural

fashion under the leadership of Philip Johnson, a small but remarkable building in upstate New York quietly forged an important new direction, dealing with issues that would become increasingly urgent in coming decades. The Hooker Ofice Building (1980), later known as the Occidental Chemical Building, by Cannon Design, is a nine-story cube situated along the Niagara River in Niagara Falls, New York. [4.11 + 4.12] The deining feature of this building is its doubleskin glass curtain wall. The project’s dual goals of energy eficiency and maximization of views led the architects to the concept of a double-envelope. [4.13] Maximizing glass area on the facades would provide the desired views and decrease necessity for artiicial lighting. The inherent problem of heat loss during winter would be addressed by creating an insulating air cavity between two walls of glass. The potential for overheating during summer would be diminished by incorporating adjustable sunshade louvers and natural ventilation in the cavity. Using solar cells, the louvers track the sun, adjusting automatically (with manual override) to maintain optimum solar control. The outer and inner skins, separated by a space of 4 feet (1.2 meters), comprise simple curtain walls with white-painted extruded-aluminum mullions on 5-foot (1.5-meter) centers. A catwalk within the cavity provides access at each level for maintenance. The outer skin incorporates green-tinted insulating glass, while the inner is loor-to-ceiling clear glass. [4.14] A review in Progressive Architecture three years after the building’s completion found it to be an “energy tour de force.” The expected mechanical systems contract had been cut nearly in half, the building came in under the owner’s original budget, and the gas-ired boiler had never been used for heat.13 The Hooker Ofice Building’s double-skin curtain wall was incredibly prescient. With dramatic results, it intelligently combined Le Corbusier’s earlier visions of the neutralizing wall and the brise-soleil. Unfortunately, due to apparent neglect and lack of tenants, the building has fallen into disrepair. It still stands, however, as an important precedent for architects struggling to resolve the sometimes dueling demands of experiential quality and energy eficiency. In naming Jean Nouvel the Pritzker Prize Laureate of 2008, the jury cited the architect’s “courageous pursuit of new ideas and his challenge of accepted norms in order

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4.12

4.11 4.11 + 4.12 Hooker Office Building, Niagara Falls, New York, Cannon Design, 1980

4.13 Typical floor plan 4.14 Wall section

4.14

4.13

to stretch the boundaries of the ield.” 14 These qualities are apparent in the project that irst brought Nouvel to international attention: the Arab World Institute (1987) in Paris.15 [4.15] Built as part of the Grand Projets program initiated by French president François Mitterand in the early 1980s, the institute is best known for its unique and highly complex curtain wall design. On the south facade of the building, Nouvel deploys a sun-shading device that is integral with the curtain wall and imbues it with a character that is not merely functionalist but also symbolic and poetic. The curtain wall itself consists of conventional double-pane insulating glass, set within prefabricated story-high units of extruded aluminum framing and suspended outside the building’s structural frame. Behind the insulating glass, however, is a unique layer of shutter mechanisms, similar in operation to those in a camera lens. These shutters, or diaphragms, were originally equipped with photocells that measured the amount of sunlight striking the glass, automatically opening or closing the shutters to maintain optimal interior conditions. On the interior side of the curtain wall, the shutter mechanisms are protected by a layer of monolithic clear glass that can be opened for maintenance access. The articulation of the shutters within the glass simultaneously references traditional Arabic latticework decoration, known as moucharabieh, while responding to the environmental conditions of a south-facing facade, achieving both through the introduction of high-tech gadgetry. The eventual malfunctioning of the shutter system, with its hundreds of

thousands of moving parts, was perhaps inevitable. Many of the diaphragms no longer move at all, due in part to limited maintenance budgets, and those that do move are now controlled by a central computer rather than the original photocells.16 Despite such setbacks, the Arab World Institute—like the Hooker Ofice Building before it— was an important experiment, promoting the notion of an intelligent curtain wall system that could automatically respond to changing environmental conditions while presenting a unique aesthetic expression. Nouvel’s approach is characterized by experimentation and a faith in contemporary solutions. He has said: My interest has always been in an architecture which relects the modernity of our epoch as opposed to the rethinking of historical references. My work deals with what is happening now—our techniques and materials, what we are capable of doing today. 17 Another inluential project by Nouvel, in which he explicitly explores the techniques, materiality, and potential immateriality of the glass curtain wall, is the headquarters for the Cartier Foundation (1994) in Paris. [4.16] This eight-story steel-framed building houses a ground loor art gallery with ofices above and parking below. The design is an interesting exploration of layered space, and it plays with the visual effects of alternating transparency and relectivity. The building itself is set back from the street and enclosed with a curtain wall of clear insulating glass. Retractable fabric blinds are hung outside

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4.16 Arab World Institute, Paris, France, Jean Nouvel, 1987

4.15

of the glass to control solar heat gain and glare. [4.17] The glass walls extend horizontally and vertically beyond the bounds of the interior space, creating free-loating planes of glass. Another freestanding glass curtain wall, similar in module and materiality, is located along the sidewalk, literally mirroring the building wall beyond it and creating an exterior space enclosed on two sides by glass. The result of this series of parallel curtain walls is an intriguing and ambiguous visual appearance—one is not certain which walls enclose space and which do not. The building suggests an afinity with the work of artist Dan Graham, whose steel and glass pavilions likewise explore the effects of transparency and relectivity on the experience of space.18 At the Cartier Foundation, these effects draw passersby into the site to explore the ground-loor gallery and courtyards, which are open to the public. The curtain wall is thus employed not only for the enclosure of a building but also for rhetorical effect, exploiting the glass curtain wall’s ability to physically divide while visually connecting disparate spaces. The conditions of transparency and relectivity dominated architectural discourse on building envelopes for much of the twentieth century, motivated by technical as well as aesthetic and experiential impulses. By the end of the century, however, there was a palpable interest among certain architects to work with the more complicated condition of translucency. This tendency was given oficial recognition by the Museum of Modern Art in New York City, with its 1995 exhibition Light Construction, featuring several projects

from around the world that explore concepts of luminescence in architecture and art. In many of these projects, various glass fabrication techniques—acid-etching, sandblasting, laminating, and casting—were used to transform glass from an “invisible” transparent surface to a material with depth and presence, one that does not simply transmit or relect light but collects and scatters it, producing a diffuse glow and hazy shadows. The idea of a translucent glass skin is certainly not without precedent in modern architecture. Earlier examples include the Maison de Verre (1932) in Paris by Pierre Chareau and Bernard Bijvoet, the Museum of Modern Art (1939) in New York City by Philip S. Goodwin and Edward Durrell Stone, and the Johnson Wax Building Research Tower (1951) in Racine, Wisconsin, by Frank Lloyd Wright. [4.18 + 4.19] Two buildings from the late 1990s stand out as innovative reinterpretations of this tradition: the Kunsthaus (1997) in Bregenz, Austria, by Peter Zumthor, and the Kursaal Auditorium and Congress Center (1999) in San Sebastián, Spain, by Rafael Moneo. The Kunsthaus is a contemporary art museum located near the shore of Lake Constance. [4.20 + 4.21] The building envelope is composed of two layers: an outer skin of translucent glass, which stands about 3 feet (90 centimeters) in front of an inner wall of concrete and glass. The outer layer, wrapping around all four sides of the building, is constructed of hundreds of identical panels of laminated glass. The panels are supported not by continuous frames but by intermittent stainless-steel angles at

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4.16 + 4.17 Fondation Cartier, Paris, France, Jean Nouvel, 1994

4.16

4.17

the top and bottom corners of each panel. The glass, which has been given an acidetched surface treatment, is arranged in a shinglelike manner, with the top and one side of each panel tilted behind the edges of the adjacent panels. Because the entire building is covered with these translucent glass “shingles,” there are no direct views into the building from the outside. Rather, there is the ambiguous suggestion of what lies beyond the surface—shadows of the ine steel substructure that supports the outer skin, faint indications of the concrete wall behind, and the diffuse glow of interior lighting at night. The Kunsthaus was among the irst buildings to use an exterior application of acid-etched glass, produced by pouring a chemical bath onto its surface for a predetermined amount of time to create a microscopically roughened surface to scatter light rays and transform the normally relective glass to a matte inish. Of the external character of the curtain wall, Zumthor wrote, “It absorbs the changing light of the sky, the haze of the lake; it relects light and color and gives an intimation of its inner life according to the angle of vision, the daylight and the weather.” 19 The interior spaces of the Kunsthaus are the true beneiciaries of Zumthor’s ingenious approach to the manipulation of daylight. The walls of the galleries are made of concrete, while the ceilings consist entirely of suspended acidetched glass panels. Above each ceiling is an eight-foot tall cavity with perimeter clerestory glass that transmits natural daylight from the outer glass curtain wall to the translucent ceiling, creating a glowing effect

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4.18 Museum of Modern Art, New York, New York, Philip S. Goodwin and Edward Durrell Stone, 1939

4.19 Johnson Wax Research Tower, Racine, Wisonsin, Frank Lloyd Wright, 1951

4.18

4.19

that changes with external environmental conditions. The result is subtle yet powerful, serving the function of displaying art while also creating an indirect connection to the outside world. The Kursaal Auditorium and Congress Center by Rafael Moneo occupies a prominent site in the seaside town of San Sebastián, Spain, where the city grid, the Urumea River, and the Bay of Biscay converge. In response to this dramatic setting, Moneo conceived the building as an element of the landscape, like “two gigantic rocks stranded at the mouth of the river, forming part of the landscape, rather than belonging to the city.” 20 The Kursaal consists of two prismatic volumes, one containing a large concert hall and the other a smaller auditorium; they are essentially buildings within a building. [4.22] The concert hall and auditorium each sit within a larger shell, clad almost entirely in a unique curtain wall system of translucent glass panels. [4.23] Like the Kunsthaus, the Kursaal’s envelope is a double skin. A cage of load-bearing structural steel framework, approximately eight feet (2.4 meters) deep from inside to out, supports an exterior skin of concave glass planks and an interior skin of lat, sandblasted low-iron glass. Complex combinations of different glass treatments and surfaces were necessary to achieve the intended effects. The outer glass skin is a composite of two different glass types, bent and laminated together, and supported by horizontal aluminum mullions anchored to the steel structure. The outer layer in the laminated assembly is composed of luted textured glass, produced

by heating and passing the glass over patterned ceramic rollers to impress the ribbed proile, while the inner is a low-ironcontent glass with a sandblasted surface treatment. The appearance of the curtain wall changes dramatically with its atmospheric context—in direct sun it becomes opaque and solid; with sunlight behind it, it mysteriously reveals its depth in shadow; at night it glows, relecting off the waters of the river and sea. [4.24] In a 1997 Architecture magazine article, the curtain wall is identiied as “an architect’s most substantial design outlet,” the part of the building design in which architects take their most creative liberties.21 This sentiment relects the growing menu of glass products and surface treatments available from fabricators, allowing architects to customize and ine-tune the performance and aesthetic effect of the curtain wall. The LVMH Tower (1999), in New York City, is emblematic of this phenomenon. Designed by Atelier Christian de Portzamparc in association with the Hillier Group, the LVMH Tower is a twenty-ive-story steel-framed building. Its ofices and showrooms are contained behind a complex skin of folded planes and varying glass types. [4.25] In the New Yorker, Paul Goldberger called it the city’s “irst important small skyscraper in more than a generation,” remarking that the glass curtain wall “has a sculptural, emotional resonance that is very rarely achieved.” 22 This sculptural quality is the result of a combination of two primary strategies: a geometrically complex form and a palette of unique glass treatments. The curtain

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4.20 + 4.21 Kunsthaus, Bregenz, Austria, Peter Zumthor, 1997

4.22 Kunsthaus, section

4.22

4.20

4.21

wall (totaling approximately 45,000 square feet, or 4,200 square meters) consists of prefabricated units framed by extrudedaluminum mullions in a grid that warps and twists to follow the geometry of the facade. [4.26] In addition to regular clear glass, the curtain wall incorporates blue- and greentinted glass, as well as ultra-clear low-iron glass. These base materials are further enhanced with surface treatments: custompatterned sandblasting, ceramic frit dot patterns, and low-E coatings. In some areas, spandrels are completely eliminated in favor of loor-to-loor vision glass, made possible by the installation of sprinkler heads in the ceiling, located just inside the glazing. The LVMH Tower established a tradition of innovative, experimental curtain wall architecture among luxury goods companies, to be followed by a number of notable buildings in the early twenty-irst century: Herzog and de Meuron’s Prada Flagship Store (2003) in Tokyo, SANAA’s Dior Building (2004) in Tokyo, and Kengo Kuma’s LVMH Building (2004) in Osaka. [4.27–4.28] In the early twenty-irst century, the issue of sustainability increasingly pervades our culture. In architecture, the concept encompasses a broad range of issues, including energy eficiency, responsible utilization of resources, and responsiveness to local climate, durability, and the creation of healthy environments. As the envelope of choice for many buildings, the curtain wall has a speciic role to play in this developing paradigm. In assessing its current role, it is instructive to return to an inluential essay from 1981.

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4.23 + 4.24 Kursaal Congress Center, San Sebastian, Spain, Rafael Moneo, 1999

4.23

4.24

In “A Wall for All Seasons,” the architects Mike Davies and Richard Rogers give a critical reassessment of what could be called the modern architect’s long “love affair” with glass and transparency.23 Following the rise in public awareness of ecology as a science in the 1960s and the energy crises of the 1970s, the authors noted that architects must recognize the inherent environmental problems, such as excessive heat gain and loss, associated with widespread use of glass in certain climates. They argued, although Mies’s early experiments in glass architecture maintained an aesthetic appeal for architects, “We were caught admiring the concept but with our technological panties around our knees.” 24 They posed a series of critical questions about the ideal of glass architecture and its emerging problems:

would rely on the development of new highperformance products with much greater thermal resistance. Although not yet realized to the extent called for by Davies and Rogers, the idea of interactivity in the building envelope has become a key element in current concepts of the intelligent facade. As opposed to older notions of glass skin as static and inert—typiied by Mies’s 1920s projects as well as the relective, hermetically-sealed single glass skins of 1970s ofice towers—a new incarnation of the glass wall has emerged in which the facade is designed to adapt automatically and intelligently in response to external and internal environmental conditions. In their 2003 book, Tower and Ofice, the architects Iñaki Ábalos and Juan Herreros describe the current transformation of the curtain wall from a passive barrier to an active system:

Mies’ wonderwall was heavily under attack. Must we say goodbye to glass? Can we never return to the transparent skin? Has the pendulum begun to swing back again towards the leaded lights in the massive walls of yesteryear? Can we stave off the problem by greater feats of ingenuity? Can we ever evolve a new architecture based upon intelligent passive energy design?25

In recent decades, the modernist glass skin— absolute, thin, dematerialized, unique and passive—has given way to another concept of wall, one that is subjective, thick, palpable like landscape, double-layered, and active from the point of view of energy. . . . It is the site at which glass, climate control, and the external environment assume congruent and interactive roles.26

Davies and Rogers proposed a new formulation of the glass wall, which they called a polyvalent wall, that would dynamically respond to changing environmental conditions. New technologies, they believed, would forge the way. The authors also predicted that the future of architectural glass

Glass is thus conceived not as a single distinct element but as one component in a system of enclosure. In such a system, the goal is for the low of energy to be controlled in both directions (inward and outward) to maximize internal comfort and minimize energy usage. The main components often

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4.25 4.25 + 4.26 LVMH Tower, New York, New York, Atelier Christian de Portzamparc in association with the Hillier Group, 1999

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4.26

include a double-skin glass envelope with variable sun-shading or diffusing elements and operable ventilators, and can include power-generating components such as photovoltaic cells or wind turbines. In addition to the buildings mentioned earlier, examples of multilayered facades may be found in buildings such as Foster + Partner’s Business Promotion Centre (1993) in Duisburg, Germany; the Renzo Piano Building Workshop’s Debis Headquarters Building (1997) in Berlin; Murphy/Jahn Architect’s Deutsche Post Tower (2003) in Bonn, Germany; and in several of the case studies included in this book. These new facade systems are often integrated directly with the building’s mechanical systems to create a holistic, eficient building response to climate and energy. It should be recognized, however, that even the highly sophisticated double-skin glass curtain walls of recent years often do not measure up, in terms of performance, to the alternative of highly insulated opaque walls.27 Nevertheless, in the spirit of architectural futurism (and

therefore in the tradition of Paul Scheerbart), in the 2002 book Intelligent Skins, Michael Wigginton and Jude Harris predict, “The intelligent facade will be one of the principal elements in the building of the future.” 28 Indeed, many architects today continue to work collaboratively with engineers and building scientists toward deining and realizing the intelligent facade, within the everpresent constraints of available technology, constructability, and cost. In an era increasingly deined by a sense of impending environmental crisis, the aesthetic dissolution of the wall has given way to a rethinking of priorities, a rebuilding of the wall, and a critical new role for glass as a material. The Genzyme Center (2003) in Cambridge, Massachusetts, is a twelve-story ofice building that boldly addresses some of these issues in an integrated fashion. Working with a consultant team and an enlightened developer and tenant, Behnisch Architekten conceived the building as an opportunity to implement green technologies in the service of not only energy eficiency

Part I: A History of the Curtain Wall as Concept and Construct

4.27

but also enhanced user experience and economic return. The design strategies include a double-skin glass curtain wall with automated sunshade blinds, roof-mounted heliostats that relect sunlight into a central atrium, and photovoltaic arrays for supplemental electricity generation. The interior spaces are lit primarily by daylight entering through either the perimeter curtain wall or the atrium, and photo-sensors automatically dim the light ixtures when daylighting is suficient. The double-skin curtain wall is used mainly on the west and south facades, with a 4-foot (1.2-meter) interstitial air cavity acting as a buffer between interior and exterior. In winter solar radiation heats the air cavity, while in the summer it is naturally ventilated. Operable windows are used throughout the curtain wall, and, on cool summer nights, the windows can be automatically opened by a central building management system to purge accumulated heat from the building. Working together, these systems are projected to reduce the building’s overall energy cost by 41 percent.29 The Genzyme Center was well received within the architectural ield as an innovative prototype. The building achieved a LEED

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4.28

Platinum rating from the U.S. Green Building Council and was selected as an AIA Top Ten Green Project for 2004. Peter Davey, in Architectural Review, called the Genzyme Center “an inspiring shift in the evolution of the ofice building type, more inventive and integrated than almost anything yet built.” 30 As evidenced by the Genzyme Center and other recent high-proile projects, among contemporary architects and engineers there is a renewed interest in the concept of sustainable architecture. The signiicant improvement of energy eficiency has become one of the primary goals in contemporary curtain wall design; however, as William McDonough points out, “Being less bad (or more eficient) is not necessarily being good.”31 It is likely that we will soon see a major shift in emphasis, from designing buildings that are simply more energy eficient to conceiving and implementing new technologies that allow buildings to actually sustainably generate energy (making a positive difference and not simply a less negative one), and it can be expected that the building envelope, as the interface between exterior and interior environments, will continue to play an essential role in this pursuit.

4.27 Prada Flagship Store, Tokyo, Japan, Herzog and de Meuron, 2003

4.28 Christian Dior Omotesando Building, Tokyo, Japan, SANAA, 2004

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Endnotes 1 “Bold and Direct, Using Metal in a Strong, Basic Way,” Architectural Record, July 1964, 136–137. 2 Ibid., 140. 3 This is according to a Kinney Vacuum Coating advertisement in the 1966 Sweets Catalog. The advertisement also features an image of the John Deere & Company Headquarters. 4 See Patrick Loughran, Falling Glass: Problems and Solutions in Contemporary Architecure (Boston: Birkhäuser, 2003), 115–116. 5 Ibid., 119. 6 Ibid., 121. 7 William Marlin, “Some Relections on the John Hancock Tower,” Architectural Record, June 1977, 123. 8 Marvin Trachtenberg and Isabelle Hyman, Architecture: From Prehistory to Post-Modernism (New York: Henry N. Abrams, 1986), 546. 9 “World’s Tallest Silicone-Glazed Curtain Wall,” Buildings (December 1984), 36. 10 See Christopher Olson, “Dramatic Geometry Challenges Project Team,” Building Design & Construction, September 1987, 102–106. 11 William Curtis, “Principle v. Pastiche: Perspectives on Some Recent Classicisms,” Architectural Review, August 1984, 14. 12 See Susan Doubilet, “Not Enough Said,” Progressive Architecture, February 1984, 70–75. 13 John Morris Dixon, “Glass Under Glass,” Progressive Architecture, April 1983, 82–85. 14 “Media Kit Announcing the 2008 Pritzker Architecture Prize,” http://www.pritzkerprize. com/full_new_site/nouvel/mediareleases/08_ media_kit.pdf, 3. 15 An extensive and insightful analysis of Nouvel’s work in Paris can be found in Fierro, The Glass State, 95-149. 16 See Loughran, Falling Glass, 88. 17 “Media Kit Announcing the 2008 Pritzker Architecture Prize,” 3. 18 This connection is also observed by Fierro in The Glass State, 117.

19 Peter Zumthor, Kunsthaus Bregenz (Ostildern: Hatje, 1999), 13. 20 José Rafael Moneo, The Freedom of the Architect (Ann Arbor, Mich.: University of Michigan Press, 2002), 30. 21 Anne C. Sullivan, “Customizing the Curtain Wall,” Architecture, January 1997, 124. 22 Paul Goldberger, “The Sky Line: Dior’s New House,” the New Yorker, January 31, 2000, 88. 23 Mike Davies and Richard Rogers, “A Wall for All Seasons,” RIBA Journal 88, no. 2 (February 1981): 55–57. 24 Ibid., 55. 25 Ibid., 55. 26 Ábalos and Herreros, Tower and Ofice, 40. 27 See John Straube, “A Critical Review of the Use of Double Facades for Ofice Buildings in Cool Humid Climates,” Journal of Building Enclosure Design (Winter 2007): 48–52. Straube inds that double facades provide a transparent all-glass aesthetic at signiicant cost; other, less expensive solutions, such as a reduction in the area of glazing, are just as technically valid if not more so. 28 Michael Wigginton and Jude Harris, Intelligent Skins (Oxford: Butterworth-Heinemann, 2002), 43. 29 U.S. Green Building Council, http://leedcasestudies.usgbc.org/energy cfm?ProjectID=274. 30 Peter Davey, “Luminous Paradigm,” Architectural Review, April 2004, 64. 31 William McDonough and Michael Braungart, “Eco-Effectiveness: A New Design Strategy,” Sustainable Architecture White Papers (New York: Earth Pledge Foundation, 2000), 3.

Essay Title

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Part II: Performance and Technique

5 Curtain Wall System Design

6 The Building Envelope as Selective Filter

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66

5

Curtain Wall System Design

5.1

Curtain Wall System Design

5.2

5.1 Curtain wall as framework, incorporating multiple variations in material and form 5.2 Glass supported by aluminum mullions, with external glazing cap running horizontally and structural silicone sealant running vertically 5.3 Glass supported by countersunk stainlesssteel point fittings

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5.3

In contemporary practice, the curtain wall is typically conceived as a system—that is, as a coordinated assemblage of components designed to perform in a speciied way. The relative success or failure of a curtain wall, in terms of both aesthetics and technical performance, may often be traced to the selection and detailing of its components. Following the irst large-scale experiments with metal frames in the 1950s, a curtain wall industry emerged that, through continual research and development, has helped advance the technology and codify its materials and methodologies.1 This has, in turn, led to the increasing sophistication and variety in curtain wall systems that characterizes the current ield. Today, the successful design of a curtain wall system requires extensive knowledge of materials and appropriate detailing; an accurate assessment of the building’s anticipated environmental conditions (both interior and exterior); a comprehensive understanding of the required performance; and a clear strategy for the relationship of the curtain wall to the building structure. Given the complexity of most contemporary systems, architects often approach the design process with a strategy of collaboration, consulting closely with a team of experts that may include facade specialists, engineers, and, in some cases, curtain wall fabricators and contractors. In general terms, the curtain wall is essentially a framework that can incorporate multiple variations in materials, form, and function. [5.1] Despite the great variety of expression, most curtain walls are based on fundamental principles of design,

utilizing a hierarchy of frames and panels. The main components are typically mullions, inill panels, and anchors. The vertical and horizontal mullions—usually fabricated out of extruded aluminum, due to its relatively high strength-to-weight ratio—form the structural frame of the curtain wall and are analogous to the building’s structural frame of columns and beams. Although variations are common, the primary mullions typically span vertically from one loor to the next, with intermediate horizontal mullions spanning between the verticals. In other words, the mullions form the framework in which the inill panels—glass, metal, stone, or other materials—are set. The proper detailing of the joint between the inill material and the mullion is essential. [5.2 + 5.3] Glass is most often held in its frame with continuous rubber gaskets or silicone seals, or alternatively by point ittings drilled into the glass. Metal and stone panels may require secondary anchor clips or other means of attachment to support the weight of the panel, while also relying on gaskets or seals to create a watertight joint. Inill panels may be classiied as either vision or spandrel panels, depending on the level of transparency and the desire for views through the curtain wall. While vision panels obviously rely on glass, spandrel panels may be glass, metal, stone, terra-cotta, or nearly any other opaque material, usually backed with an air cavity, a sealed back pan, and insulation. The network of assembled frames and inill panels is connected to the primary building structure by an anchor system. The typical curtain wall anchor,

Part II: Performance and Technique

5.4

consisting of metal angles or channels bolted to each vertical mullion and to the edge of the loor slab, transfers wind loads and dead loads from the wall system to the building’s structural frame. The anchor must also accommodate the anticipated tolerances and movement of the structure to which it is attached, allowing adjustment in three dimensions (x, y, and z axes). Based on the extent to which the system design is unique, a curtain wall may be classiied as either standard or custom. Numerous manufacturers offer a wide variety of standard off-the-shelf curtain wall systems, the components of which may be selected from a catalog, with predetermined and pretested details.2 Such systems are generally less expensive and may offer some means of limited customization through an optional kitof-parts approach (with different glass types, mullion proiles, etc.). Standard systems are usually selected for smaller-scale or smaller-budget projects, or for curtain walls without unique performance or aesthetic requirements. Custom systems, on the other hand, are individually designed and built, usually for a single building (or a group of related buildings) with a more generous budget and more elaborate goals for technical performance or aesthetic expression. Custom systems generally require extensive testing and quality control throughout the design and construction process, while standard systems, which have been previously tested and documented by the manufacturer, require less. In addition to the custom and standard distinctions, curtain wall systems are further classiied according to their methods of

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5.5

fabrication and installation. Although hybrid combinations are possible, most curtain walls fall into one of two main categories: the stick system or the unit system. In a stick-system curtain wall, the individual components are assembled piece by piece (or stick by stick) on the construction site. [5.4] First, the primary mullions are anchored to the building structure, followed by the installation of any intermediate mullions spanning between primary members, and inally the inill panels are installed, along with other secondary components, such as shading devices or ornamental ins. Most stick systems are standard, off-the-shelf products and therefore have relatively low material cost. Another advantage of the stick system is the low expense of shipping and handling due to the ability to eficiently package and transport the separate components. The main disadvantages of the stick system derive from the method of assembly in the ield, which generally involves a slower pace, higher labor costs, and a greater potential for problems concerning the quality and precision of the work compared to factory prefabrication. Stick systems are usually limited to low- or mid-rise applications. [5.5] A unit system (or unitized) curtain wall consists of prefabricated modules that are assembled under controlled factory conditions and then shipped to the construction site and connected to preinstalled anchors on the building structure. [5.6] Although many variations are possible, a typical curtain wall unit is between 4 and 10 feet (1.2 and 3 meters) wide by one to two stories tall, anchored at each loor slab or beam.

5.4 Stick-system curtain wall, components installed piece by piece on site 5.5 Stick-system curtain wall

5.6 Unit-system curtain wall, with units prefabricated in shop, transported to site, and anchored to building structure 5.7 Installation sequence for a unit-system curtain wall 5.8 Installation of unitsystem curtain wall at Trump Tower, in Chicago, Illinois

Curtain Wall System Design

69

5.6

5.7

5.8

Because each curtain wall unit arrives fully glazed on site, with all framing and inill panels complete, ield labor is minimized. The advantages of the unit system therefore include greater quality control during fabrication and quicker on-site installation, as well as a greater ability to accommodate building movement caused by delection or wind loads. The disadvantages of the unit system include higher shipping costs and the necessity for sequential installation. (Because of the way that one unit interlocks with the next, the units must be installed in a particular sequence; whereas stick systems permit more freedom.) Unit systems are typically selected for high-rise and highvolume curtain walls and, in some cases, for smaller buildings with generous budgets. [5.7 + 5.8] The differences in assembly methods between these two systems become evident in the details. Typical mullion plans for a stick-system and a unit-system curtain wall reveal key detailing strategies. Both mullions described here consist of extruded-aluminum sections that span vertically from one loor to the next, spaced ive feet (1.5 meters) on center, with an inill of double-pane insulating glass. As noted previously, aluminum has a high strength-to-weight ratio (desirable when trying to create a lightweight wall); it also accepts a wide variety of inishes such as painting and anodizing and is well suited for the process of extrusion, in which heated aluminum is forced through a series of dies to create a speciied shape. The sticksystem mullion [5.9] is extruded in a rectangular box shape with recessed channels

Part II: Performance and Technique

5.9

that accept continuous gaskets along the front edge. After this mullion has been anchored to the loor slab and horizontal mullions have been installed, the glass panel is set in place and held against the mullion by an extruded-aluminum pressure plate that is intermittently screwed into the mullion, exerting pressure through gaskets and mechanically ixing the glass to the frame. The pressure plate is often separated from the mullion itself by a plastic or rubber thermal break, intended to limit heat loss. On the exterior, the pressure plate can be covered by a cap (also made of aluminum), which snaps onto the plate, concealing the fasteners and forming the exterior inished surface of the mullion. Whereas the sticksystem mullion is a single, uniied member, the unit-system mullion is composed of two adjacent unit frames that interlock to form the vertical member. [5.10] Known as a dynamic (or split) mullion, this two-part extruded-aluminum mullion allows some relative movement between adjacent units (for thermal expansion and contraction) and gives the system greater lexibility in general. Gaskets are used to provide a seal at joints where two unit frames come together. The detail shown here incorporates four-sided structural silicone glazing, a method in which the glass is essentially “glued” onto its frame using high-strength silicone in lieu of an exterior pressure plate and cap. In addition to the aesthetic effect of a continuous, lush glass surface, this method limits the potential for heat loss through the metal frame by minimizing the amount of metal exposed to the exterior. Obviously, a high

70

5.10

degree of precision and quality control is required in the application of the silicone sealant, and therefore the use of four-sided structural glazing is limited to unit systems that are prefabricated in controlled factory conditions and is not advisable for ieldassembled stick systems. Unit systems may also utilize the more traditional, captured glazing method with a pressure plate and exterior cap. Extruded aluminum is the framing material of choice for most curtain walls, but multiple variations are possible. [5.11] Although curtain walls can incorporate a wide array of inill materials, glass is by far the most common. The speciication and detailing of glass in curtain walls has become quite complex in recent years, as the industry, responding to a broad range of technical and aesthetic demands, has begun to offer an ever-expanding menu of products and fabrication options. An important distinction can be made between primary production and secondary fabrication of architectural glass. The production of glass refers to the primary process of making large sheets of glass, which are then fabricated—via secondary processes—into various types. For instance, the vast majority of architectural glass today is produced by the loat process, a fully mechanized procedure in which the raw materials of glass (silica sand, soda ash, lime, and other ingredients) are melted at a temperature of about 3,000°F and then loated onto a bath of molten tin, forming a continuous ribbon that is eventually cooled and cut into large sheets of lat glass.3 By varying the mineral composition of the raw materials, loat glass can be produced in a range of

5.9 Stick-system curtain wall mullion, typical plan detail 5.10 Unit-system curtain wall mullion, typical plan detail

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71

5.11

5.12

5.11 Possible variations in mullion material, from left: steel T, steel pipe, aluminum, and wood 5.12 Glass-fabrication options, from left: monolithic glass, laminated glass, insulating glass, laminated insulating glass, and triple-pane insulating glass. 5.13 Glass laminated with photovoltaic cells

5.13

integral color tints—from regular clear glass (which has a slightly greenish tint) to shades of bronze, gray, blue, and green. In low-iron (or “water white”) glass, the greenish tint of regular clear glass is eliminated by reducing the iron content in the batch of raw materials. In addition to various tints, the loat process produces sheets of varying thicknesses. Standard thicknesses for architectural glass range from an eighth of an inch (three millimeters) to three-quarters of an inch (nineteen millimeters). The glass sheets produced by the loat method can then be fabricated into numerous other products through such secondary processes as laminating, heat-treating, coating, insulating, ceramic fritting, acid-etching, sandblasting, bending, or nearly any combination of the above. [5.12] Laminated glass consists of two or more pieces of glass permanently bonded together with an interlayer of cured liquid resin or plasticized sheet material (polyvinyl butyral or polycarbonate) fused to the glass through heat and pressure. Laminated glass generally qualiies as safety glazing, because if the glass breaks, the fragments tend to adhere to the interlayer (reducing the potential for dangerous fall-out) and the interlayer resists the passage of objects or people through the glass plane. This is why most building codes require the use of laminated glass in overhead glazing applications such as skylights and glass loors. An added beneit of the common interlayer of polyvinyl butyral is its ability to block a high percentage of the sun’s ultraviolet (UV) rays, which can cause damage to artwork, fabrics, and paper.

Laminated glass, therefore, is often used in museums, galleries, and libraries, even when conditions do not require safety glass. For custom aesthetic applications, interlayers can be printed with photographic images, patterns, colors, or text. The laminating process can also be used to encase photovoltaic cells between two glass panes for electricity generation. [5.13] Like many secondary processes, glass lamination is labor intensive and adds signiicant cost. Glass produced by the loat process is also known as annealed glass. Through the secondary processes of heat-treating, the strength characteristics of loat glass may be improved, resulting in either heatstrengthened (HS) or fully tempered (FT) glass. This process involves heating a piece of glass to a set temperature and then cooling it again very quickly under controlled conditions, creating a compression envelope around the glass surface and edges, with an internal tension layer at the center. This results in increased glass strength and load resistance. HS glass has approximately two times the strength of annealed glass of the same thickness. FT glass (also known as toughened glass), which is produced in a method similar to that of HS glass but is cooled much quicker, has about four times the strength of annealed glass of the same thickness. HS and FT glass thus offer means of increasing glass strength without increasing thickness. When FT glass is broken, it breaks into many small fragments with dull edges (as opposed to the large, sharp pieces of annealed and HS glass) and therefore usually qualiies as safety glazing. [5.14]

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5.14

In its original state, loat glass, which may be referred to as monolithic or single-pane glass, is inherently ineficient in terms of thermal insulation, and except in mild climates without extreme temperature variations, it is insuficient for most architectural applications. Insulating glass units consist of two or more panes of glass separated by spacers to create sealed interstitial air cavities, ranging from a quarter to three-quarters of an inch in depth, greatly improving thermal performance. The typical coniguration includes an aluminum spacer illed with desiccant and sealed to each pane with a primary vapor seal of polyisobutylene. A secondary seal of structural silicone holds the two panes together. Because the metal spacer is a good conductor of heat, the edges of an insulating glass unit are the most vulnerable to unwanted heat loss. When improved performance is required, alternative “warm edge” spacers with better insulating properties than aluminum, such as stainless steel and thermoplastic spacers, may be speciied. Insulating glass units may also incorporate various glass surface treatments to further transform the basic loat glass. Relective and/or low-emissivity (low-E) coatings can signiicantly improve the solar-heat-gain coeficient and thermal insulating properties of glass. Ceramic frit comes in assorted colors and can be silk-screened in custom patterns (most often, using dots or lines) then baked, to permanently fuse with the glass surface, creating different aesthetic effects as well as increased solar shading. Sandblasting and acid-etching can be used to create textured, translucent surfaces that diffuse light and

5.15

Curtain Wall System Design

73

5.14 Typical breakage pattern of fully tempered glass

obscure direct vision through the glass. [5.15] All of these secondary fabrication processes have an effect on the cost and the available sizes of glass. The maximum size of a particular product is usually limited by some combination of the manufacturing equipment on which it is fabricated, the weight of the inished product, or restrictions on transporting the inal product. This survey of glass-fabrication options illustrates that the design of a curtain wall system requires a broad knowledge of materials, component fabrication, and installation methodologies. In addition, the designer must also consider the performance characteristics of each component during the life of the building. In each curtain wall system described above, the speciic conigurations of the mullions and inill panels depend on a number of technical factors. The required dimensions of a mullion, for instance, must be calculated based on the material chosen, the spacing of the mullions, their overall span, and wind loads. The minimum glass thickness is inluenced by the dimensions of the individual pane, the glass type, its method of edge support, and wind loads. The minimum width of a bead of structural silicone sealant is determined by the rated strength of the silicone, the size of the pane, and the wind loads. Beyond these primary structural concerns, the design of a curtain wall system must also respond to a complex set of environmental performance parameters, which will be discussed more fully in the next chapter.

5.15 Insulating glass with custom-patterned ceramic frit silkscreen (suggesting foliage), Utretcht University Library, Utrecht, the Netherlands, Wiel Arets Architects, 2004

Endnotes 1 In the United States, the American Architectural Manufacturers Association has published a number of advisory documents related to curtain wall design and construction, including design guidelines, model speciications, testing procedures, and performance standards. Other related standards speciically relevant to curtain wall design have been developed by the American National Standards Institute, the American Society for Testing and Materials, and the Glass Association of North America. Most countries have counterpart organizations that set standards for the design and testing of curtain walls. 2 Examples include manufacturers such as Architectural Glazing Technologies, EFCO, Kawneer, Oldcastle Glass, Schüco, United States Aluminum, and Visionwall. 3 See Bradford McKee, “Float Glass,” Architect, July 2007, 68–75.

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6

The Building Envelope as Selective Filter BUILDING ENVELOPE INTERFACE

Meso-environment (architectural)

6.1 The building envelope as selective filter, adapted from James Marston Fitch, 1948

Macro-environment (terrestrial) winter insolation (infrared)

winter heating

radiant convected

winter air temperature (still air) winter winds Thermal

summer conditions

cooled air dehumidified air circulated air

summer insolation summer air temperature (still air)

Atmospheric

summer breeze winter humidity

summer humidity precipitation

Aqueous

household odors pleasant unpleasant

odors

dust and pollution view out privacy (view in) daylight glare artificial illumination

artificial illumination

productive sound noise (waste sound)

noise

Luminous

Sonic

inhabitants visitors intruders vermin and insects pollens microorganisms nuclear radiation

nuclear pollution

Biological

The Building Envelope As Selective Filter

75

Because of the continuous luctuation of all environmental factors across time, the building wall must be visualized not as a simple barrier but rather as a selective, permeable membrane with the capacity to admit, reject and/or ilter any of these environmental factors. All building walls have always acted in this fashion, of course. Modern scientiic knowledge and technical competence merely make possible much higher, more elegant and precise levels of performance than previously.1 James Marston Fitch’s depiction of the building wall as a selective two-way ilter in American Building, irst published in 1948, remains a useful analogy, particularly given today’s growing concerns about energy eficiency and sustainability. Fitch envisioned the building envelope as analogous to the skin of the human body, which adaptively responds to the external environment in an effort to maintain optimal internal conditions. But the capacity of the human body to accommodate the range of climatic conditions evident in the natural world is of course limited, and we therefore require what Fitch termed an ameliorating “third element.” 2 This third element, which he calls a “mesoenvironment,” acts as an interface between the microenvironment of the body and the macroenvironment of the external world. [6.1] There are two primary manifestations of the meso-environment: clothing and buildings. As Fitch explains, each can be tailored to meet the requirements of speciic people in particular situations (and, by the way, each may be subject to the whims of fashion). Clothing and buildings simply operate at different scales: “One protects the individual only while the other shelters social processes as well.” 3 The way in which the meso-environment, as the boundary between the micro and macro, modulates itself in response to changing conditions— its relative success or failure given speciied parameters and goals—may be considered its performance, and for contemporary curtain walls, performance is a key concept with important consequences for the way the system is designed and built. The curtain wall should act as a selective ilter, purposefully controlling the low of heat, light, air, water, and sound, as well as the subsequent impact that these elements

exert on interior spaces. Examples of such iltering include the control of views into and out of a building, the transmission of natural light, the ventilation of interiors, and the regulation of rainwater. At the most basic level of performance, however, a curtain wall should be structurally sound. The components of the curtain wall system must be designed and built to resist anticipated loads, such as those induced by wind, seismic activity, and the potential impact of objects or people against the wall. The most signiicant load on a curtain wall is often lateral wind load (except in cases where blast resistance is required). The anticipated force of wind blowing against or pulling away from a curtain wall (the design wind load) is dependent on a number of factors: the location and orientation of the proposed building, the size and shape of the building, the immediate context of other structures or natural features, the surrounding landscape, and the measured history of wind activity at the site. Sometimes the design wind load is speciied by local building code; often, however, it is calculated according to civil engineering principles or determined by testing a physical scale model of the proposed building in a wind tunnel. Wind loads on a single building may vary greatly in different locations: higher wind loads are often present at the top of a building and at the corners of walls, as opposed to more centralized areas. Due to orientation, one face or side of a building may see signiicantly higher or lower wind loads than other faces. Because the materials of the curtain wall tend to be relatively lexible and not rigid, delection (not strength) usually governs the resistance to wind. In other words, the curtain wall will likely reach an unacceptable level of delection under wind loading before it will fail structurally. Therefore, most curtain wall speciications limit the allowable delection of the curtain wall mullions and inill panels to a certain dimension, based on the span of the member. For example, vertical mullions spanning from one loor to the next are typically limited to a maximum delection of L/175, where L equals the loor-to-loor height.4 So, for a curtain wall spanning 10 feet (3 meters) vertically, the maximum allowable delection of the mullion would be 10 feet/175 = 0.0571 feet, or roughly 5/8 inch.

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COMPARISON OF INSULATING GLASS PERFORMANCE

All examples assume 1/4"thick inner and outer glass panes with 1/2" air space

wind pressure

10’

maximum deflection

INSULATING GLASS TYPE

VISIBLE LIGHT TRANSMITTANCE

VISIBLE LIGHT REFLECTANCE

SHGC

WINTER U-VALUE

Clear glass, uncoated

79%

14%

0.70

0.47

Gray glass, uncoated

41%

7%

0.48

0.47

Clear glass with reflective coating

12%

33%

0.18

0.40

Clear glass with low-e coating

70%

11%

0.38

0.29

Gray glass with low-e coating

35%

6%

0.24

0.29

Clear glass with low-e coating and ceramic frit pattern (50%)

44%

22%

0.26

0.29

Clear glass, uncoated, + argon fill

0.45

Clear glass, low-e + argon fill

0.25

Triple glazing, clear glass, uncoated

0.31

Triple glazing, clear glass low-e + argon fill

0.14

6.2

6.3

[6.2] The curtain wall mullion in this case must be designed to resist the design wind load while delecting less than ive-eighths of an inch, a task that has implications for the material choice, the dimensions of the mullion itself, and the spacing of mullions on the facade. Higher wind loads may mean that mullions should be reinforced with steel or spaced closer together, or that a deeper mullion section is required. As glass tends to dominate the contemporary curtain wall, the overall thermal performance of the wall often comes down to the selection and detailing of the glass panel, which can be an inherently poor thermal insulator. The various glass treatments discussed in the previous chapter can greatly affect the way that glass conducts heat and transmits or rejects solar energy. Relective and low-E coatings, consisting of microscopically thin layers of metals deposited on the surface, signiicantly improve the shading coeficient and thermal insulating properties of glass. Obviously, the relective coatings popular in the 1970s acted basically as mirrors, blocking unwanted solar energy from entering the building but also preventing the transmission of much visible light, thus eliminating the transparency so long associated with glass. But a newer generation of specialized metallic coatings, with improved performance, a more neutral appearance, and higher visible light transmittance, became available in the 1980s and 1990s. These coatings selectively ilter (transmit or relect) the various wavelengths of sunlight to ine-tune the facade’s performance. Currently, a doublepane clear insulating glass unit with a high-

performance, neutral low-E coating can attain a U-value as low as 0.29, as compared to 0.47 for uncoated insulating glass or 1.02 for uncoated monolithic (single-pane) glass.5 That same low-E unit can achieve a solarheat-gain coeficient of 0.38, as compared to 0.70 for an uncoated unit, and it can be further improved through the use of tinted glass substrates.6 [6.3] Of course, most curtain walls are not entirely glass, and, in fact, the mullions that frame and support the glass are a potentially onerous source of unwanted heat transmission. The thermal break—a means of physically separating metal components that are exposed to the exterior from those exposed to the interior—is in certain climates an essential detail in a curtain wall mullion. In the design phase, architects may use thermal simulation software to test various conigurations of glass and mullions based on expected environmental conditions. [6.4] In addition to specifying appropriate glass products and mullion conigurations, designers continue to experiment with multilayered glass skins as a means of creating a more sophisticated selective ilter. The main concept in this type of system is the creation of an air plenum, between two layers of glass, that acts as a moderating buffer between interior and exterior environmental conditions. The two layers may be positioned on either side of a single mullion, separated by several inches, or they may exist as two separately framed curtain walls, spaced several feet apart. In periods when interior heating is required, the air cavity remains sealed and the air is heated naturally by solar gain. This warmed air can then

6.2 Curtain wall deflection diagram 6.3 Comparison of insulating glass performance

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6.4

6.4 Thermal modeling of curtain wall mullion, to determine degree of heat loss and susceptibility to condensation

be used either as a passive buffer, which reduces the need for mechanical heating, or as preheated intake air for the HVAC system. During cooling periods, the air cavity can be ventilated to provide a continuous low of fresh air that can be routed into the interiors. The area between the layers of glass creates a convenient and protected location for sunshades, which can be adjusted seasonally or daily to provide the optimal balance of views and shading, blocking unwanted solar energy before it strikes the inner glass wall and making large expanses of glass more feasible from an energy standpoint. The multilayer approach also offers the beneit of improved sound control. While such active systems represent a major advantage over passive, single-skin precedents in meeting demands for both occupant comfort and energy eficiency, recent research suggests that the double skin is not technically superior to the less expensive alternative of reducing the amount of glass in the wall while increasing the area of opaque superinsulated wall.7 As architects and engineers continue to experiment with the active double wall and exploit its potential coordination and integration with a building’s HVAC systems, it can be expected that further innovation will continue to yield better performance. Regardless of the type of system chosen, it is common to subject a custom curtain wall to a series of physical mock-up tests to measure its performance under simulated environmental conditions prior to inal installation on site. Such trials typically take place at a specialized independent laboratory and are

observed by the architect, owner, and contractor. The goal is to conirm the performance of the curtain wall with respect to a speciic set of criteria. The full-scale mock-up, usually about two stories in height and one or two structural bays in width, is built with the same materials and methods that will be used in the inal construction. It is subjected to a series of tests, which typically include resistance to air and water leakage, structural performance under wind load, and condensation resistance. A standard sequence may include the following: 1. Static Air Iniltration (ASTM E283): the rate of air leakage through the curtain wall 2. Static Water Penetration (ASTM E331): the amount of water leakage through the curtain wall 3. Dynamic Water Penetration (AAMA 501): water leakage under high wind conditions 4. Structural Performance (ASTM E330): delection using air-pressure differential to simulate wind load 5. Thermal Cycling (AAMA 501): simulates the effects of temperature variation 6. Condensation Resistance (AAMA 1503): assesses the likelihood of condensation occurring within or on the curtain wall 7. Lateral and Interstory Movement (AAMA 501): the mock-up frame is moved laterally to simulate differential movement of the building structure under wind or seismic loads [6.5] The mock-up’s response to each test is measured precisely and compared to the speciied criteria. If the model performs as

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78

6.5 Airplane engine and propeller used to simulate high winds during a curtain wall mock-up test

6.5

expected, it passes; otherwise, remediation measures are required, and the system must be modiied so that it can pass a retest. The process, though costly in terms of money and time, is a valuable tool, particularly for custom systems. Potential problems in performance and aesthetics can be identiied well in advance of on-site installation, giving the design team and the fabricator an opportunity to resolve ificulties and to more fully ensure a successful installation phase and inal product. The performance of a curtain wall is inluenced equally by the quality of its design and construction. An inadequately designed curtain wall will likely fail, even if it is fabricated and installed well; a well-designed curtain wall may fail if it is fabricated and installed poorly. For these reasons, the curtain wall design process begins with extensive component research, engineering, detailing, and preliminary testing, and continues onto the construction site with a battery of ield tests and inspections to ensure proper performance of the wall, once it is installed. During prefabrication of a unit system, for instance, it is common for the design team to periodically visit the factory to inspect progress on the curtain wall. Testing the components,

such as the adhesion of structural silicone, may be conducted in the factory during this period. Once on-site installation has begun, the curtain wall is subjected regularly to ield testing—standardized procedures that measure the amount of water and air iniltration through the wall, as compared to speciied allowable amounts. Any problems found during such tests must be solved, with the remediation measures then applied similarly to all other areas of the wall. There is an increasing expectation that architecture should respond intelligently to local climatic conditions, conserving rather than wasting resources, and that it should achieve, as Fitch described, “much higher, more elegant and precise levels of performance.” As the primary interface between the exterior macroenvironment and the interior meso-environment, the building envelope has an essential role to play in this pursuit. The achievement of a high-performance curtain wall, moving beyond the status quo, relies on the expertise of the design team, the clear delineation of performance parameters and criteria, an intense process of testing and inspection, and a spirit of experimentation and technological innovation.

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79

Endnotes 1 James Marston Fitch, American Building: The Environmental Forces That Shape It (Boston: Houghton Miflin, 1972), 9. First published in 1948. 2 Ibid., 8. 3 Ibid., 9. 4 L/175 is an industry standard, although some architects prefer a more stringent limitation of L/240. Also, the maximum delection of a curtain wall mullion is often limited to L/175 or 3/4 inch (1.9 centimeters), whichever is less, as 3/4 inch is considered the highest acceptable delection of a typical mullion, regardless of load. 5 The U-value is a measure of heat gain or loss through glass due to differences between indoor and outdoor temperatures; it measures the insulating value of glass. The lower the U-value, the better the insulating performance. The U-value unit is BTU/(hr × ft 2 ×˚F) or in metric W/(m2 × ˚K). 6 The solar heat gain coeficient (SHGC) of glass measures the portion of directly transmitted and absorbed solar energy that enters into the building’s interior. A higher SHGC indicates more heat gain. 7 See John Straube, “A Critical Review of the Use of Double Facades for Ofice Buildings in Cool Humid Climates,” Journal of Building Enclosure Design (Winter 2007): 48–52.

Part III: Case Studies

Introduction

The following case studies present twenty-four recently constructed buildings with innovative curtain walls. The selected projects are geographically diverse and range in scale from two to fifty-two stories tall. They encompass a broad range of building types: museums, libraries, office buildings, educational and research centers, residential towers, government buildings, and religious institutions. Although the curtain wall design of each building is unique, there are broad themes that many of the projects share. Several curtain walls address performance issues through multiple layering, with double-skin walls, external shading devices, and operable components. Some projects illustrate the challenges of designing a curtain wall for a geometrically complex building form. In several projects, there is a clear desire to break away from the traditional vertical plane by introducing angled facades and tilted glass. Some buildings exploit the potential of unusual curtain wall materials, such as wood and translucent stone, while others employ standard materials in novel ways: the glass, for instance, is tinted, silkscreened with custom patterns, or formed into channel shapes. Kenneth Frampton writes: The full tectonic potential of any building stems from its capacity to articulate both the poetic and the cognitive aspects of its substance….Thus the tectonic stands in opposition to the current tendency to deprecate detailing in favor of the overall image.1 The buildings chosen for this study embody this duality of poetic design and technical, detail-oriented rigor. Each of these buildings engages in image-making, clearly seeking to create a distinctive visual impact, but they equally pursue experiential and performance-driven objectives, illustrating the depth of technical knowledge of materials and fabrication methodologies required for successful innovation in curtain wall design and construction. In addition to photographs and general building information, the tectonic character of each curtain wall is represented on the following pages with a detailed elevation-plan-section composite drawing that delineates system components, materials, key dimensions, and the relationship between wall and building structure.

1 Kenneth Frampton, Studies in Tectonic Culture (Cambridge, Mass.: MIT Press, 1995), 26.

Case Study Title

The New 42ndd Street Studios/ p.86

84

Melvin J. and Claire Levine Hall / p.94

One Omotesando / p.100

William J. Clinton Presidential Center / p.106

Green-Wood Mausoleum / p.112 LVMH Osaka / p.118

Torre Agbar / p.140

Seattle Public Library / p.126

Terrence Donnelly Centre for Cellular and Bimolecular Research / p.132 Skirkanich Hall / p.162

Netherlands Institute for Sound and Vision / p.154 Torre Cube / p.148

Case Study Title

85

ATLAS Building / p.184

Biomedical Science Research Building / p.176 Nelson-Atkins Museum of Art / p.198 Trutec Building / p.168

Spertus Institute of Jewish Studies / p.214

Blue Tower / p.190

United States Federal Building / p.222

Yale Sculpture Building / p.230

The New York Times Building / p.206

100 Eleventh Avenue / p.244

Cathedral of Christ the Light / p.236

166 Perry Street / p.250

Case Study Title

86

Case Study Title

87

The New 42nd Street Studios New York, NY United States

Curtain Wall Stick system with extruded-aluminum mullions and low-E coated insulating glass units; on the south facade, an external layer of perforated stainless-steel louver blades set within an armature of painted steel Program A total of 84,000 square feet (approximately 7,804 square meters) of space, including fourteen rehearsal studios for music, dance, and theater; office space for performing-arts groups; a 199-seat experimental theater; and ground-floor retail Architect Platt Byard Dovell White Client New 42nd Street, Inc. Curtain Wall Consultant Heitmann and Associates Structural Engineer Anastos Engineering Associates MEP Engineer Goldman Copeland Associates Exterior Lighting Designer Vortex Lighting (Anne Militello) Completion Date 2000

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Located in New York City’s Times Square Theater District, this ten-story tower serves as the headquarters for the nonprofit arts group New 42nd Street. It was built as part of a major redevelopment plan to transform the block through the revitalization of existing theaters and an infusion of new commercial and arts-related initiatives. The public face of the building is the south facade, where the curtain wall is conceived as a multilayered and multifunctional system of enclosure. Cantilevered floor slabs support a continuous glass-and-aluminum curtain wall, providing a floor-to-ceiling glass envelope at each level. By day, the building’s offices

and rehearsal spaces are flooded with natural light, diffused through an outer layer of perforated stainless-steel louvers that start about 6 feet (1.8 meters) above each floor and extend upward to the next level. A grid of painted steel framing members support the louvers, which are held approximately 3 feet (0.9 meters) in front of the glass wall on horizontal steel outriggers anchored to each floor slab. The curtain wall also incorporates adjustable translucent shades for glare control, operable windows for natural ventilation, and an exterior maintenance catwalk. The redevelopment guidelines for 42nd Street required a significant amount of

1

1 Typical floor plan 2 South elevation

2

exterior lighting and signage to maintain the character of the district. In response, Platt Byard Dovell White—working with lighting designer Anne Militello of Vortex Lighting—transformed the south facade into a building-scale luminaire, or complete lighting unit. The stainless-steel louvers act as a canvas onto which a nightly computercontrolled light show is projected, turning the facade into a shimmering, abstract collage of color. This use of integrated architectural illumination offered an alternative to the advertising-dominated theme-park feel that pervades the district.

The New 42nd Street Studios

89

3 Detail of nighttime illumination 4 Exterior view, from southeast

3

4

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5 Partial elevation

5' 6" (1.52 m)

6 Plan

The New 42nd Street Studios

91

H

17' 4" (5.28 m)

A

E

G

B F

C

D

I

J

7 Section

A Perforated ground

F Out-swinging

stainless-steel blades B Painted steel

operable window G Extruded-aluminum

vertical strut C Steel-grate mainte-

nance catwalk on steel outrigger

mullion H Adjustable

translucent shade I

Raised dance floor on concrete slab

J

Cantilevered steel beam

D Exterior light fixtures E Insulating glass with

low-E coating

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8

The New 42nd Street Studios

93

10

9

8 Multilayered facade components 9 View of upper floors, from southwest 10 Detail of southeast corner 11 Interior view of curtain wall in dance studio

11

Case Study Title

94

Case Study Title

95

Melvin J. and Claire Levine Hall Philadelphia, PA United States

Curtain wall Custom active double-skin unit system with prefabricated extruded-aluminum unit frames, external double-pane insulating glass, and internal singlepane glass Program Offices, laboratories, meeting spaces, and an auditorium for the Department of Computer and Information Science at the University of Pennsylvania Architect KieranTimberlake Associates Client University of Pennsylvania School of Engineering and Applied Science Structural Engineer CVM Structural Engineers Civil Engineer Barton and Martin Engineers MEP Engineer Vanderweil Engineers Energy Consultant Arup Completion Date 2001

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96

Melvin J. and Claire Levine Hall is one of the first large-scale applications of an active double-wall concept in the United States. A desire for transparency and openness— a counterpoint to the masonry aesthetic of the surrounding campus—led to the design of an all-glass curtain wall. To avoid the use of dark-tinted or reflective glass and large areas of spandrel, as would normally be required by the energy code, KieranTimberlake researched the potential of using an active double-skin to maintain transparency and mitigate thermal issues inherent in conventional single-skin curtain walls. The final design called for a custom unit system incorporating various configurations of extruded-aluminum frames with two

layers of glass: an outer double-pane insulating unit and a single inner pane. The two layers are separated by a 6-inch (15centimeter) plenum, through which air circulates; it is preheated by the sun (in winter) before being transferred to the HVAC system. The air cavity houses electronically controlled blinds to reduce heat gain in summer. The fully prefabricated unit system was installed on site in seven weeks. Credit must also go to the client, the University of Pennsylvania, for recognizing the benefits of an unusually high-performance, energyefficient building envelope and for understanding that the higher construction cost of such a system would be balanced by lower energy use and operating costs over the life of the building.

1

2

1 View through curtain wall, from interior 2 View of interior

Melvin J. and Claire Levine Hall

97

3 Installation of curtain wall units 4 View of west elevation 5 Catalog of custom curtain wall unit types

3

4

5

A1A Qty. 8

A4

Qty. 8

B6

Qty.11

A1A Qty. 1

A5

Qty. 7

B6A Qty. 4

A2 Qty. 10

B1

A2A Qty. 1

A3

Qty. 9

Qty. 9

B2

Qty. 19

B4

Qty. 7

B6B Qty. 3

B7

Qty. 3

B8

Qty. 3

A3A Qty. 1

B5

B9

Qty. 7

Qty. 3

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6 Partial elevation

7' (2.13 m)

7 Plan

4' 4" (1.32 m)

Melvin J. and Claire Levine Hall

99

G

H E D

C

14' (4.27 m)

A

8 Section

B

I F

A Outer skin: clear insu-

lating glass with low-E coating

E Exhaust air duct (from

curtain wall cavity) F Extruded-aluminum

unit frame

B Inner skin: monolithic

glass (sandblasted in some areas) C Adjustable interior

cavity blind (electronic) D Adjustable room shade

(manual)

G Finished floor on rein-

forced concrete slab H Fire-safe insulation

at slab edge I

Suspended ceiling

Case Study Title

100

Case Study Title

101

One Omotesando Tokyo, Japan

Curtain Wall Custom stick system incorporating monolithic glass and external vertical wood fins Program A total of 83,000 square feet (4,459 square meters) of office and retail space for a fashion company Architect Kengo Kuma and Associates Client LVMH Structural Engineer Oak Structural Design Office Mechanical Engineer P. T. Morimura and Associates Completion Date 2003

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This seven-story building stands at the entrance to Omotesando Avenue. Lined on both sides with tall Zelkova trees, the avenue leads to the city’s oldest Shinto shrine, the Meiji Shrine. The architect sought to design a building that would reflect the natural warmth of surrounding greenery and reference Japan’s long tradition of building with wood. The curtain wall is constructed out of extruded-aluminum mullions that span vertically from floor to floor and support the monolithic tempered glass. Horizontal joints between glass panels are minimized through the use of structural silicone glazing, while the vertical joints are emphasized

with protruding tapered fins of laminated wood (Japanese Larch) attached to each vertical mullion. These fins, measuring approximately 18 inches (0.5 meters) deep, act to stiffen the vertical mullions and lend an unusual texture and color to the curtain wall. Additionally, the fins act as solar-shading devices, reducing the amount of direct sunlight that reaches the floor-to-ceiling glass panels. Because of fire-safety concerns, Tokyo’s building code prohibits the use of wood on exterior walls in dense urban areas; however, the fins were permitted due to the unusual provision of water sprinkler heads spaced at regular intervals along the exterior surface of the curtain wall.

1 View from Omotesando Avenue

2 View from interior 3 Detail of wood fin attachment at curtain wall 4 Exterior view

1

One Omotesando

103

3

2

4

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5 Partial elevation

2' (0.60 m)

6 Plan

One Omotesando

105

B

C

F

A

E

D

13' 9" (4.2 m)

G

7 Section

A Laminated wood fin

E Adjustable shade

B Monolithic tempered

F Raised floor on

glass C Extruded-aluminum

mullion D Glass soffit

concrete slab G Suspended ceiling

Case Study Title

106

Case Study Title

107

William J. Clinton Presidential Center Little Rock, AK United States

Curtain Wall The primary, west-facing curtain wall: a custom double-layered stick system with an inner curtain wall of low-iron insulating glass supported by steel-tube framing, with an outer skin of point-supported laminated glass with a printed interlayer Program A presidential library with permanent and temporary exhibition spaces, an education and media center, an event space, a cafe, and a rooftop residential apartment Architect Polshek Partnership Architects Client William J. Clinton Presidential Center Associate Architects Polk Stanley Rowland Curzon Porter Architects; Witsell Evans Rasco Architects; Woods Caradine Architects Curtain Wall Consultant R. A. Heintges and Associates Structural Engineer Leslie E. Robertson Associates MEP Engineers Flack and Kurtz; Cromwell Architects Engineers LEED Consultants Steven Winter Associates; Rocky Mountain Institute Completion Date 2004

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The William J. Clinton Presidential Center is located in a public park along the south bank of the Arkansas River and within walking distance of downtown. The bulk of the 165,000-square-foot (15,329-squaremeter) building is elevated in a linear form, cantilevered toward the river and supported by massive exposed-steel trusses, inspired by an adjacent centuryold railroad bridge. Unusual among presidential libraries, the design embraces modern aesthetics and technology and offers a contemporary approach to the articulation of architecture, which is perhaps most apparent in the design of the exterior envelope.

The client’s objectives included an open and accessible museum and a commitment to environmental responsibility; the building earned a LEED Silver certification. The main facade is the west elevation, which faces toward an entry plaza, with downtown Little Rock visible in the distance. The curtain wall consists primarily of transparent glass, which allows for expansive views and natural lighting. At night, activities within the center are on display through the glass walls. The double-height curtain wall at the exhibition wing is composed of two walls of glass on either side of a porchlike space measuring 10 feet (3 meters) deep. The inner wall of low-iron, low-E coated insulating

glass forms the true weather envelope of the building, while an outer rainscreen of laminated glass provides solar protection and sound insulation. The glass of the inner wall is framed by extruded-aluminum glazing adapters mounted to horizontal steel tubes suspended, by steel tension cables, from the roof. The glass of the outer wall is laminated with an interlayer of custom-printed, thin blackand-white lines that allow views through while deflecting a portion of the solar energy striking the surface. Countersunk stainless-steel point fittings (or spiders) support the glass panels at each corner and are, in turn, supported by horizontal steel tubes that are suspended from above, similar to the inner wall.

1

1 Floor plan, level four 2 East-west section, looking south

2

William J. Clinton Presidential Center

109

3

4

3 South elevation 4 View from south 5 Space between outer and inner glass walls, looking north toward the river

5

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6 Partial elevation

10' (3.05 m)

7 Plan

William J. Clinton Presidential Center

111

A

B C

D J

D

E

F

5' 4" (1.63 m)

G

H

I

8 Section

A Laminated low-iron

F Laminated low-iron

tempered glass

insulating glass with low-E coating

B Countersunk stainless-

steel bolt and spider fitting

G Steel and aluminum

mullion with stainlesssteel cladding

C Painted steel tube D Stainless-steel threaded

dead-load rod

H Steel truss I

Tempered glass railing

J

Adjustable shades

E Steel column

Case Study Title

112

Case Study Title

113

Green-Wood Mausoleum Brooklyn, NY United States

Curtain Wall Custom hybrid system of preglazed units mounted in a shinglelike configuration onto steel mullions Program A new mausoleum facility providing burial chambers and gathering spaces within Green-Wood Cemetery Architect Platt Byard Dovell White Client Green-Wood Cemetery Structural Engineers Siracuse Engineers; Leslie E. Robertson Associates MEP Engineer Joseph R. Loring and Associates Completion Date 2004

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114

Established in 1838, Green-Wood Cemetery was designated as a National Historic Landmark in 2006. The new five-story mausoleum provides 2,000 additional burial chambers. The design is based on a strong yet simple dichotomy of solidity and lightness. The crypts are organized into three vertical stacks encased in stoneclad walls; these massive volumes are earthbound, cut into the steep hillside, and they are organized around two sky-lit atria containing stairs and seating areas. The rear wall of each atrium is formed by a four-story interior waterfall, which is echoed at the front in a cascading glass curtain wall that provides abundant natural light and views of the landscape. The fluidity, openness, and airiness of

the atriums balance the heaviness of the burial chambers. The glass curtain wall is composed of a custom system of monolithic clear glass panels angled, in section, like shingles, with the lower edge of each panel cantilevering several inches beyond the frame. Structural silicone sealant holds the glass in place and minimizes the external expression of the supporting framework. The glass is preglazed onto extrudedaluminum frames, which are then anchored to an internal framework of exposed horizontal and vertical steel mullions suspended from each floor slab. The exposed, freefloating edges and precise detailing of the panels contribute to the overall sense of lightness.

1

2

1 Southeast elevation 2 Cantilevered monolithic glass

Green-Wood Mausoleum

115

3

3 Interior view of curtain wall at top floor 4 Typical floor plan

4

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5 Partial elevation

7' 5" (2.26 m)

6 Plan

Green-Wood Mausoleum

117

E

F

A

C

D

4' 6" (1.37 m)

B

7 Section

A Structurally glazed

monolithic tempered glass B Extruded-aluminum

unit frame C Painted steel beam

D Painted steel column E Painted steel guardrail F Reinforced-concrete

floor slab

Case Study Title

118

Case Study Title

119

LVMH Osaka Osaka, Japan

Curtain Wall Hybrid system with floor-to-floor translucent panels of laminated stone and glass preglazed to extrudedaluminum frames and mounted onto vertical steel mullions Program Ninety-thousand square feet (8,361 square meters) of office and retail space for a fashion company Architect Kengo Kuma and Associates Client LVMH Japan Group Curtain Wall Consultant Front Structural Engineer Ban Design Studio Mechanical Engineer P. T. Morimura and Associates Completion Date 2004

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Kengo Kuma and Associates’ nine-story LVMH building in Osaka, Japan, presents a building envelope of remarkable material effect; an intentional blurring of the traditional distinction between wall and window, and between stone and glass. From day to night, the curtain wall continually shifts conditions, from opacity to transparency and translucency. The curtain wall incorporates 5/³² -inchthick (4 millimeters) onyx slabs laminated between sheets of clear glass. These slices of stone are thin enough to transmit diffused light. During the day, they appear solid and opaque from the exterior, while allowing natural light to filter through to the interior; at night, the stone panels glow from within, revealing their translucent

nature, thanks to fluorescent cove light fixtures integrated into each mullion. The monolithic stone cube transforms into a lantern. To provide opportunities for views through the curtain wall, the stoneand-glass composite panels alternate, in a ratio of two to one, with laminated glass units utilizing a polyester interlayer printed with a pattern that resembles the grain of onyx. While the panels simulate the texture and color of the stone, they are primarily transparent. Both types of glass panels extend vertically from floor to floor—without spandrels—and are preglazed onto minimal frames of extruded aluminum, which are, in turn, mounted onto vertical mullions of built-up steel.

1 Section 2 Typical floor plan

1

2

LVMH

121

3+4 Interior views

3

4

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5 Partial elevation

3' (0.91 m)

6 Plan

123

B

F

2 ft. 11 in. (0.89 m)

C

G E

H

13' 2" (4 m)

LVMH

D

A

B

7 Section

A Laminated panel:

glass, translucent stone, glass B Laminated glass with

printed interlayer C Extruded-aluminum

frame D Vertical steel mullions

with integral light fixture

E Adjustable blinds F Raised floor on

concrete slab G Fireproofed steel

beam H Suspended ceiling

Part III: Case Studies

8 Night view

8

124

LVMH

125

9 Curtain wall parapet 10 View from street

9

10

Case Study Title

126

Case Study Title

127

Seattle Public Library Seattle, WA United States

Curtain Wall Custom stick system of steel and aluminum framing members arranged in a diamond-grid configuration supporting low-E coated, laminated insulating glass. Program Seattle’s central public library containing book stacks, reading rooms, meeting rooms, a children’s center, administrative offices, an auditorium, and parking Architects Office for Metropolitan Architecture (OMA); LMN Architects Client Seattle Public Library Facade Consultants Dewhurst Macfarlane and Partners; Front Structural Engineers Arup; Magnusson Klemencic Associates MEP Engineer Arup Civil Engineer Magnusson Klemencic Associates Completion Date 2004

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128

Sited within the dense urban context of downtown Seattle, the 412,000-squarefoot (38,276-square-meter) Central Library owes its aggressively distinctive character to two defining design moves: the stacking and shifting of building masses into an unexpected prismatic form, and a custom curtain wall system that wraps continuously around all sides of the building. The curtain wall is composed of diamondshaped panels of insulating glass, measuring approximately 4 feet (1.2 meters) per side, set within a diagrid framework of steel and aluminum. As the primary cladding of the building, the glass units were designed for high performance and include a lami-

nated pane for safety and UV protection; a low-E coating; krypton gas fill for increased thermal performance; and, in areas of the building subject to intense summer sun, an expanded aluminum mesh interlayer, which acts as a system of micro louvers to reduce solar heat gain while maintaining views. The glass is supported by extrudedaluminum glazing adapters attached either to seismic structural-steel framing members (on sloped faces) or to I-beam-shaped mullions of extruded aluminum (on vertical faces). It is held in place by exterior aluminum glazing caps. The building skin contributes not only to the exterior character of the building—signaling a willingness to

forego traditional concepts of library architecture—but also to the interior experience of the end users, who encounter the diagrid enclosure from different vantage points throughout the eleven-story building. In recognition of the complexity and overall importance of the building envelope, an early bid package and contractor selection process for the curtain wall allowed the architects to collaborate with the curtain wall manufacturer (the German firm Seele) throughout the design and construction phases, ensuring that architectural design goals and stringent performance criteria were met.

1 Unfolded elevation 2 Locations of glass with metal mesh interlayer

1

2

Seattle Public Library

129

3 Southwest corner 4 Third-floor interior 5 Interior view from fourth floor

3

4

5

6

6 Interior view of curtain wall mounted on seismic steel framing

Part III: Case Studies

7 Partial elevation

8 Plan

130

Seattle Public Library

131

D

F

E G

A

16' 5" (5 m)

B

C

8 Section

A Laminated insulating

glass with low-E coating, argon fill, and mesh interlayer B Extruded-aluminum

glazing adapter C Extruded-aluminum

diagonal mullion D Structural steel

E Formed aluminum

gutter with stainlesssteel snow fence and drain F Raised floor G Concrete slab on

deck

Case Study

132

Case Study

133

Terrence Donnelly Centre for Cellular and Biomolecular Research Toronto,Ontario Canada

Curtain Wall The south facade: a double-skin glass curtain wall, with an outer layer of monolithic glass and an inner layer of insulating glass, each framed by extruded-aluminum mullions and separated by an air space Program A human genome research facility with laboratories, offices, and common spaces, including multistory interior gardens Architects architectsAlliance; Behnisch Architekten Structural Engineer Yolles Partnership Mechanical/Electrical Engineer HH Angus & Associates Completion Date 2005

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The twelve-story Terrence Donnelly Centre for Cellular and Biomolecular Research, located at the University of Toronto’s St. George campus, is a high-performance building that achieves impressive levels of energy efficiency and—with airy, lightfilled spaces throughout—attention to occupant comfort. The building responds intelligently to its climate and orientation with an enclosure system that presents an open face to the campus and adapts to changing environmental conditions. At the same time, it strikes a balance between automated and individually controlled devices. The 248,000-square-foot (23,039-squaremeter) research facility is organized with laboratories to the east, circulation to the west, and principal researchers’ offices

to the south, facing a landscaped entry plaza. It is this south-facing wall that is the most technologically innovative. Offices here are enclosed with a double-skin glass curtain wall, framed by extruded-aluminum mullions, that provides a high degree of acoustic, solar, and thermal control. The outer skin of monolithic glass is separated from the inner layer of insulating glass by an air space of 2.5 feet (0.8 meters), containing retractable perforated aluminum sunshade louvers to reduce solar heat gain and redirect daylight into the building. The outer skin incorporates operable louvers at the top and bottom to ventilate the cavity, while the inner wall has operable windows to naturally ventilate the offices.

1

2

In winter the air cavity remains sealed, as the sun naturally heats the air to create a buffer between the interior and exterior; in summer the cavity is freely ventilated. A computerized building system automatically adjusts the sunshades for optimal solar protection, although each individual occupant may override the system, as desired. Likewise, occupants can control the degree of ventilation in each office. When a window is opened, a sensor automatically switches off the heating and cooling supply to that space, thereby increasing energy efficiency and avoiding waste.

Terrence Donnelly Centre for Cellular and Biomolecular Research

135

4 Interior view

3 4

1 Tenth-floor plan 2 View from southwest 3 Double-skin curtain wall 4 Southwest corner 5 Interior view

5

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136

6 Partial elevation

4' (1.22 m)

7 Plan

Terrence Donnelly Centre for Cellular and Biomolecular Research

137

A G B

I C

D

E H F

13' 4" (4.06 m)

J

8 Section

A Monolithic

G Insulating glass in

extruded-aluminum unit frame

tempered glass B Stainless-steel

patch fitting

H Aluminum spandrel

with insulation

C Mechanical

ventilation damper

I

Finished floor over cantilevered concrete slab

J

Suspended ceiling

D Laminated tempered

glass floor E Steel outrigger F

Automated blinds

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Terrence Donnelly Centre for Cellular and Biomolecular Research

139

9 West elevation at night

Case Study

140

Case Study

141

Torre Agbar Barcelona, Spain

Curtain Wall Custom system of clear and translucent glass louvers suspended on extrudedaluminum framing members, in front of a load-bearing reinforced-concrete wall with punched windows Program Office headquarters for a local water company Architect Ateliers Jean Nouvel Client Layetana Inmuebles S.L. Facade Consultants Xavier Ferres (Biosca Botey); Alain Bony; Arnauld de Bussierre Structural Engineers R. Brufau; A. Obiol MEP Engineer Gepro Lighting Consultant Yann Kersalé Completion Date 2005

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Housing the headquarters of Barcelona’s water utility, Torre Agbar is a thirty-one-story, bullet-shaped tower sited within a new commercial development in Plaça Glòries. Jean Nouvel’s design was conceived as an expression of the fluidity of water and its interaction with light. The architect likens the exterior to an enormous geyser of water under continuous pressure. In stark contrast to the popular formulation of the skyscraper as a glass-clad, steel- framed box, Torre Agbar employs a reinforced- concrete bearing-wall structure, defined in plan and section by gentle curves pierced with 4,500 individual window openings. The bearing wall, which in conjunction with an internal structural core

ensures a column-free interior, ranges in thickness from 19 inches (0.5 meters) at the base to twelve inches at the twenty-ninth floor, where it ends; the upper six floors are framed in steel and clad in glass. The exterior of the bearing wall is divided into a continuous 1-square-meter (10.8square-foot) grid covered in insulation and corrugated aluminum panels painted various shades of red, blue, green, yellow, and white. An apparently random pattern of punched openings in the wall provides views, daylight, and natural ventilation, incorporating insulating glass in extrudedaluminum window frames. The bearing wall is encased in a continuous external skin of clear and translucent laminated

1

1 Typical floor plan 2 Exterior detail

2

safety-glass louvers set at various angles. These louvers are mounted on vertical rails of anodized extruded aluminum that are suspended from the concrete wall on aluminum brackets at each floor level. As compared to other all-glass curtain walls, the combination of louvers, a thick external wall, and a high ratio of solid wall to window create a more energy-efficient building. The result of this unique buildingenvelope system is an intriguing surface effect that is not merely a thin surface in the normal sense, but a multilayered surface that has a literal and metaphorical depth unlike any other skyscraper in Barcelona or elsewhere.

Torre Agbar

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3 Unrolled elevation 4 Exterior night view 5 Exterior daytime view

3

4

5

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6 Partial elevation

6' 6" (2.0 m)

7 Plan

Torre Agbar

145

B

A

G H

I

12' 2" (3.7 m)

C

D E

F

8 Section

A Laminated glass louver

F Galvanized-steel

maintenance catwalk

B Anodized extruded-

aluminum rail C Aluminum window

G Raised floor H Concrete slab on

with low-E coated insulating glass D Painted corrugated

aluminum sheet E

Mineral wool insulation over reinforcedconcrete wall

metal deck and steel beam I

Suspended ceiling

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146

Torre Agbar

147

11 9 Interior views 10 Detail of louvers 11 Installation of windows 10

12

12 Exterior view at midlevel

Case Study

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Case Study

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Torre Cube Guadalajara, Mexico

Curtain Wall Window walls with extruded-aluminum framing and floor-to-ceiling monolithic glass protected by a brise-soleil system of timber slats Program Leasable office space with underground parking Architect Estudio Carme Pinós Client Cube International Structural Engineer Luis Bozzo Completion Date 2005

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Sited in a dense office building development, Torre Cube stands out among its neighbors for its distinctive massing and material expression. The building houses approximately 50,000 square feet (4,645 square meters) of space on sixteen levels and is organized around a central atrium that is open to the sky. Three massive concrete cores—containing vertical circulation, service spaces, and ductwork—form the main vertical structure of the building. From these cores, steel girders are cantilevered to support the column-free offices, which feature floor-to-ceiling glazing on three sides. The glass is contained within frames of extruded aluminum, span-

ning between the floor slabs. A system of external brise-soleil panels protects the building from excessive heat gain. They are composed of heat-treated pine slats, set in frames of welded steel that are suspended two feet in front of the glass wall (with a maintenance catwalk in-between). The varied spacing and natural color variation of the wood slats give the facade an organic warmth that is unusual for office-building construction. Some of the eye-level brise-soleil panels slide aside on tracks, allowing for unimpeded views and increased daylighting when desired. Sliding glass doors within the window wall provide access to the brise-soleil panels

and allow natural ventilation in the offices. Additionally, on each side of the building and at different heights, three floors of office modules are eliminated to create exterior plazas and promote the free circulation of fresh air into the atrium. Because of these measures, and the mild climate of Guadalajara, no air-conditioning is required in the offices.

1 Section 2 Typical floor plan

1

2

Torre Cube

151

3

4

3 Wood screen at east elevation 4 View from southeast 5 Construction sequence

5

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6 Partial elevation

5' 5" (1.65 m)

7 Plan

153

A

B

C

D

11' 6" (3.5 m)

Torre Cube

I E F

H G J

8 Section

A Heat-treated pine strip

on steel angle frame B Vertical steel-pipe

bracing

F Steel pipe G Steel outrigger H Embedded steel

anchor plate at slab edge

C Guide track and rollers

for sliding screen D Tempered monolithic

glass in extruded-aluminum frame E

Maintenance catwalk: galvanized-steel grating

I

Raised floor on concrete slab

J Suspended ceiling

Case Study

154

Case Study

155

Netherlands Institute for Sound and Vision Hilversum, the Netherlands

Curtain Wall Custom double-layer wall with a continuous outer screen of textured, color-stained glass panels bearing abstracted scenes from Dutch television Program A 323,000-square-foot (30,007-squaremeter) media museum with interactive exhibition spaces, a public atrium, archives, offices, a museum store, workshops, a cafe, and underground parking Architect Neutelings Riedijk Architects Client Netherlands Institute for Sound and Vision Facade Consultant Jaap Drupsteen Structural Engineer Aronsohn Raadgevende Building Physics Cauberg-Huygen Raadgevende Completion Date 2006

Part III: Case Studies

Three main program elements constitute the Netherlands Institute for Sound and Vision: a series of galleries for interactive media exhibitions, a block of administrative offices, and the national archives of Dutch radio and television. These spaces are grouped around a central atrium that extends from the front to the rear of the building and from the lowest floor to the skylit roof. In a unique twist on the modernist ideal of a facade expressing the inner function of the building, the outer skin of the institute consists of a composition of glass panels imprinted with 748 specific images, or still frames, from Dutch television programs, selected from the national archives (housed inside and presumably in the collective memory of the TV-watching public). The images

156

are mostly abstracted through a blurring effect; the exact scenes are not immediately apparent, although many are discernible. The architects worked collaboratively with the graphic designer Jaap Drupsteen and the glass manufacturer Saint-Gobain to develop a method of transferring the selected film stills onto glass by CNCmilling them onto a wood panel, which was then used as a mold onto which the glass, along with colored ceramic paste, were placed and then heated. This process imparts the colored, textured image in relief onto the glass. These tempered-glass panels, measuring .375 inches (1 centimeter) thick, are used to clad all four sides of the building. They are typically glazed on two sides (top

and bottom) to steel channels, which are anchored to continuous horizontal steel tubes. The tubes are suspended from the roof above by vertical steel rods. The inner wall varies from clear insulating glass to a solid, opaque wall. At the office wing, the inner wall alternates between steel-framed insulating glass windows and precastconcrete wall panels faced with insulation and fiber-cement sheeting. In these areas, the colored outer glass is replaced in every third bay with clear glass to provide unimpeded views from the offices.

1 Section 2 Textured-glass panel at west elevation 3 East elevation 4 Interior view at atrium

1

Netherlands Institute for Sound and Vision

157

2

3

4

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5 Partial elevation

3' 11" (1.2 m)

6 Plan

159

A

B C

10' 5" (3.16 m)

Netherlands Institute for Sound and Vision

D

E

F

I

G

H

7 Section

A Custom-patterned

cast glass in pivoting steel frame

F Steel tube column G Cement-fiber panel

over mineral-fiber insulation

B Clear tempered glass

at operable vent

H Precast-concrete

C Steel suspension rod D Steel tube E Insulating glass in

thermally broken steel frame

wall panel I

Finished floor on concrete slab

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8 West elevation at night 9 Southeast corner 10 Detail of texturedglass panel

8

Netherlands Institute for Sound and Vision

161

9

10

Case Study

162

Case Study

163

Skirkanich Hall Philadelphia, PA United States

Curtain Wall Customized thermally broken stick system with angled mullions of extruded aluminum supporting clear and translucent glass panels Program Research and instructional laboratories and office space for the School of Engineering and Applied Sciences at the University of Pennsylvania Architect Tod Williams Billie Tsien Architects Client University of Pennsylvania School of Engineering and Applied Science Associate Architect Guggenheimer Architects Curtain Wall Consultant Axis Group Limited Structural Engineer Severud Associates MEP Engineer Ambrosino, Depinto & Schmeider Completion Date 2006

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The work of Tod Williams and Billie Tsien is generally remarkable for its intense focus on material expression and attention to architectural detailing. This is particularly evident in their design for Skirkanich Hall, a 58,000-square-foot (5,388-squaremeter) laboratory facility at the University of Pennsylvania. The building envelope consists mostly of standard campus architecture materials, brick and glass, but here the materials have been customized and altered from their traditional incarnations. The opaque walls are clad in custom- glazed, textured, moss-green brick that creates a sense of mass and weight. Within these solid masses, intermittent vertical openings are marked by curtain

walls with angled, shinglelike glass panels that incorporate alternating bands of transparency and translucency. Designed primarily to bring natural light into the corners of each floor, the curtain wall employs stick-built framing of painted, thermally broken extruded-aluminum mullions suspended from the face of each cast-in-place concrete floor slab. Each storyhigh mullion angles out at its base, with the bottom row of glass overlapping the top row of the level below. Through various fabrication techniques, the glass is rendered either transparent or translucent, depending on its location in section. At vision areas, from sill to ceiling, the glass is clear, low-E coated insulating glass;

1 Typical floor plan 2 East elevation

1

2

spandrels are insulating glass with translucent acid-etching on the second surface and ceramic frit on the fourth surface; and the bottom free-floating panel at each level is tempered monolithic glass with translucent acid-etching on the second surface. The lower glass panels cantilever beyond the edges of the curtain wall frame and are each supported with two countersunk stainless-steel bolts anchoring them to the vertical mullion.

Skirkanich Hall

165

3

4 3 Installation of glass in stick curtain wall system 4 Curtain wall detail 5 Interior of laboratory

5

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6 Partial elevation

3' 9" (1.14 m)

7 Plan

Skirkanich Hall

167

G

F

H

15' 6" (4.72 m)

A

D

B

E

C

8 Section

A Clear insulating glass

with low-E coating B Insulating glass with

acid etch on #2 surface and ceramic frit on #4 C Tempered monolithic

glass with acid etch on second surface D Thermally broken

extruded-aluminum mullion

E Steel bracket F Adjustable blind G Cantilevered

reinforced-concrete floor slab H Suspended

ceiling

Case Study

168

Case Study

169

Trutec Building Seoul, Korea

Curtain Wall Custom unit system with insulating glass structurally glazed to flat and projecting unit frames of extruded aluminum Program Office and showroom spaces with underground parking Architect Barkow Leibinger Architekten Client TKR Sang-Am Contact Architect Chang-Jo Architects Facade Consultants Arup Facade Engineering; Alutek Structural Engineers Schlaich Bergermann and Partner; Jeon and Lee Partners Completion Date 2006

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The Trutec Building, containing eleven floors of offices and showrooms, was one of the first buildings constructed in a new commercial development in Seoul, Korea, known as Digital Media City, intended to be a center of international business and information technology. With a limited budget and little preexisting context, the architects developed a building envelope that utilizes innovative digital fabrication techniques and is characterized by unique abstract visual effects. The curtain wall visually captures the surrounding context—whether it be the sky, cars, or other buildings—within its fragmented glass surfaces, reflecting it back in a kaleidoscope of light and color.

The curtain wall is composed of a custom prefabricated unit system framed with extruded-aluminum mullions. In order to control solar heat gain while providing a predominantly glass facade, a reflective low-E coated insulating glass is used. Within each curtain wall unit, the glass panels are divided into nonorthogonal fragments, some of which are angled slightly out of the plane of the wall. The complex facade is actually composed of just two basic unit types: one flat, two-dimensional unit; and one projecting, three-dimensional unit, which can be rotated 180 degrees to produce a third type. In order to make such variation economically feasible, the curtain wall fabricator used CNC digital

technology to precisely cut and assemble the complex three-dimensional unit frames. Barkow Leibinger Architekten successfully pairs a sculptural approach—a play with light, reflections, and perception— with technical rigor. It is this combination of aesthetic and technical exploration that results in the most innovative examples of curtain wall construction.

1 Elevations

Trutec Building

171

2 Curtain wall unit configuration diagram 3 Northwest elevation

3-way joint

4-way joint

Plan detail

2

Plan detail

3

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4 Partial elevation

8' 10" (2.7 m)

5 Plan

Trutec Building

173

A B

D C

13' 9" (4.2 m)

E

F

G

H

I

J

6 Section

A

Adjustable antiglare blind

F

Insulating glass with low-E coating

B

Steel beam with fireproofing

G

Extruded-aluminum stack joint

C

Steel column, galvanized-metal cladding

H

Floor register with convector and uplight

I

Raised floor

D

Suspended ceiling, galvanized perforatedmetal panel

J

Steel and concrete composite floor

E

CNC-cut, extruded-

aluminum mullion

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174

Trutec Building

175

7 Night view 8 Northeast elevation 9 Main entry

8

9

10 Interior view 11 Interior view with translucent shades

10

11

Case Study

176

Case Study

177

Biomedical Science Research Building Ann Arbor, MI United States

Curtain Wall A curvilinear double-skin curtain wall consisting of an outer wall of monolithic glass in a prefabricated unit system and an inner wall of insulating glass in a stick system, separated by an air space Program A 472,000-square-foot (43,850-squaremeter) building, with research laboratories, offices, conference rooms, seminar rooms, an auditorium, and a cafe Architect Polshek Partnership Architects Client University of Michigan Curtain Wall Consultant Heitmann and Associates Structural Engineer Severud Associates MEP Engineer Bard, Rao and Athanas Consulting Engineers Sustainability Consultant Buro Happold Completion Date 2006

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This research facility is sited between the University of Michigan’s main campus and its medical school, creating a new link between the two. Its primary programmatic elements are discernable in the building’s overall form. To the north, a rectilinear L-shaped block contains laboratories and support spaces, separated from the offices by a skylit atrium. The offices are arranged in an organically shaped, curvilinear band facing south, toward the street and the main campus. The laboratory block is enclosed predominantly in insulating glass and rainscreen panels of terra-cotta and stainless steel. The most innovative enclosure system is the double-skin curtain wall of the south-facing offices.

The inner curtain wall consists of a standard stick system with extruded-aluminum mullions, insulating glass, and insulated spandrel panels. The outer wall is a prefabricated unit system with frames of extruded aluminum, structurally glazed single-pane glass, and no spandrels. At curved portions, the inner wall is faceted, while the outer wall employs bent glass and curved mullions. The two walls are separated by an air space of about four feet, with the outer wall supported on steel outriggers at each mullion. The air space contains adjustable blinds, maintenance catwalks, and trackmounted movable platforms for glass cleaning. In summer, the stack effect is used to ventilate the air space; as heated

air escapes at the top of the wall, fresh air is drawn in at the bottom. In winter, the air space remains sealed and is heated by the sun, creating a buffer between disparate exterior and interior air temperatures. Compared to a conventional single-layer glass curtain wall, the double wall provides expansive views and a higher level of thermal comfort for office occupants, improved acoustical separation from the street, and lower energy use.

1 Typical floor plan

1

Biomedical Science Research Building

2

179

3

2 Installation of curtain wall 3 View west from plaza 4 Double-skin glass curtain wall at southfacing offices

4

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5 Partial elevation

9' (2.75 m)

6 Plan

Biomedical Science Research Building

181

A

B

D

C

E

15' 6" (4.72 m)

F

I

G

H

J K

7 Section

A Structurally glazed

F Extruded-aluminum

monolithic glass B Extruded-aluminum

stick-system mullion G Galvanized-steel

unit frame

maintenance catwalk

C Retractable blinds

H Steel outrigger

D Stainless-steel

I

spandrel panel with insulation E Insulating glass

with low-E coating

Concrete floor on metal deck

J Adjustable blind K Suspended ceiling

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8 Double-skin curtain wall in winter (left) and summer (right) 9 Double-skin glass curtain wall from below

8

Winter

Summer

Biomedical Science Research Building

9

183

Case Study

184

Case Study

185

ATLAS Building Wageningen, the Netherlands

Curtain Wall Stick system of extruded-aluminum mullions with low-E coated insulating vision glass and aluminum spandrel panels, installed inboard of a precastconcrete-diagrid structural frame Program Research laboratories and offices for the Environmental Sciences Group at Wageningen University Architect Rafael Viñoly Architects Associate Architect Van den Oever, Zaaijer and Partners Client Wageningen University Structural/Civil Engineer Pieters Bouwtechniek MEP Engineer Schreuder Groep Building Physics DGMR Completion Date 2006

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Located in a newly developed research district on the somewhat rural campus of Wageningen University, the seven-story ATLAS Building houses 105,000 square feet (9,755 square meters) of laboratories and office space organized around a central skylit atrium. The building presents a sculptural yet strikingly simple facade dominated by an external precast-concrete diagrid that wraps around all four sides. The exoskeleton configuration was designed by Rafael Viñoly Architects to provide flexible, column-free interior spaces that could be easily transformed and repartitioned according to future needs. Here, the relationship of structure to skin is an intriguing inversion of the typical cur-

tain wall configuration—rather than a glass skin enclosing the building structure, the building appears as a glass box set within a protective latticework of concrete. The diagrid structure also acts as an external shading device for the floor-to-ceiling glass wall installed approximately two and a half feet behind it. At each level, the wall is divided into three horizontal bands of glass, with the middle strip incorporating operable hopper windows. The curtain wall provides the interior spaces with ample daylighting, natural ventilation, and a strong visual connection to the surrounding landscape. The external space between the wall and structure contains retractable blinds for solar control and maintenance catwalks on each level.

1 West elevation 2 Interior view 3 Diagrid structure at corner 4 Maintenance catwalk between external diagrid structure and curtain wall

1

ATLAS Building

187

2

3

4

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5 Partial elevation

5' 11" (1.80 m)

6 Plan

ATLAS Building

189

A

B

H

C

I

11' 10" (3.6 m)

E G

F

D

7 Section

A Precast-concrete

F Painted extruded-

diagrid structure B Steel grate mainte-

aluminum mullion G In-swinging oper-

nance catwalk C Exterior adjustable

able window H Finished floor on

blinds

reinforced-concrete slab

D Painted aluminum

spandrel panel with insulation E Insulating glass with

low-E coating

I

Suspended ceiling

Case Study

190

Case Study

191

Blue Tower New York, NY United States

Curtain Wall A semicustom unit system with tinted insulating glass and operable windows set within frames of extruded-aluminum mullions Program Residential tower with thirty-two apartments Design Architect Bernard Tschumi Architects Executive Architect SLCE Architects Client Angelo Cosentini and John Carson Curtain Wall Consultant Israel Berger and Associates Structural Engineer Thornton Tomasetti MEP Engineers Ettinger Engineers Completion Date 2007

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Blue Tower is one of a handful of recently constructed mid-rise residential buildings now transforming the skyline of New York City’s Lower East Side. The sixteen-story, cast-in-place concrete structure contains thirty-two apartments with a total floor area of 55,000 square feet (5,110 square meters). Two aspects of the design give Blue Tower its distinctive appearance: the geometry of the building form and the expression of the curtain wall. Utilizing air rights to the adjacent site, the tower cantilevers over an existing twostory commercial building; the massing of the tower also responds creatively to

zoning setback requirements, with angled walls that slope in and out. The building is covered with approximately 4,000 pieces of glass in a prefabricated-unit-system curtain wall. The pixelated effect of the facade is achieved through the use of six different types of glass: blue- and gray-tinted insulating vision glass and four shades of blue spandrel glass. The curtain wall incorporates operable windows for natural ventilation as well as louvered vents that supply fresh air to air-conditioning units. Although based on a standard prefabricated unit system, the curtain wall has been somewhat customized through novel glass

1 North-south section

selection and unique mullion extrusions, necessary to accommodate the unusual corner geometries where sloped and vertical walls meet. The curtain wall fabricator, AGT, utilized extensive digital threedimensional modeling, CNC fabrication, and GPS site survey techniques to ensure proper detailing and installation of the geometrically complex curtain wall.

RF 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2

1

Blue Tower

193

2

3

2 Curtain wall unit installation 3 Detail at west elevation 4 Levels thirteen to sixteen

4

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5 Partial elevation

3' 4" (1.02 m)

6 Plan

Blue Tower

195

A B

F E

G

10' 4" (3.15 m)

C

D

H

7 Section

A Tinted insulating glass

with low-E coating

F

Curtain wall anchor

G

Continuous fire-safe insulation at slab edge

H

Concrete column, gypsum-board cladding

B Extruded-aluminum

stack joint C Extruded-aluminum

mullion D Operable window E Reinforced-concrete

flat slab

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8 Unfolded elevation 9 View from south

8

Blue Tower

9

197

Case Study

198

Case Study

199

The Nelson-Atkins Museum of Art Kansas City, MO United States

Curtain Wall A custom double-skin system incorporating an outer wall of translucent, sandblasted channel-glass planks separated by a 3-foot (0.9-meter) space from an inner wall of translucent laminated glass Program A 165,000-square-foot (15,329-squaremeter) addition to the original 1933 building of the Nelson-Atkins Museum that includes new permanent and special exhibition galleries, education areas, conservation facilities, meeting spaces, shops, administrative offices, and underground parking Architect Steven Holl Architects Local Architect Berkebile Nelson Immenschuh McDowell Architects Client Nelson-Atkins Museum of Art Curtain Wall Consultant R. A. Heintges and Associates Structural Engineer Guy Nordenson and Associates Associate Structural Engineer Structural Engineering Associates Mechanical Engineers Ove Arup and Partners; W. L. Cassell and Associates Lighting Consultant Renfro Design Group Completion Date 2007

Part III: Case Studies

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Steven Holl Architects’ expansion of the Nelson-Atkins Museum of Art, known as the Bloch Building, fuses the new architecture with the museum’s sprawling sculpture garden. New gallery spaces are arranged in a linear fashion along the garden, marked by five glass-clad volumes, which the architect refers to as “light-gathering lenses” that emerge from the garden landscape. The lenses incorporate a complex double-skinned glass-wall system, which provides the galleries with diffused natural light by day (modulated by computer-controlled screens within the wall cavity). The building glows from within at night, turning the lenses into largescale sculptures in their own right.

Though interrupted in some areas by bands of clear insulating glass that provide direct views inside and out, the primary curtain wall features various forms of continuous translucent glass, which react dynamically to changing light conditions throughout the day. The typical doublelayer curtain wall incorporates an outer skin of interlocking, translucent, U-shaped channel-glass planks with a sandblasted finish and translucent Okalux insulation between the planks. Because of its structural shape, channel glass is self-supporting and does not rely on mullions or any other form of vertical support, even when used in heights up to 20 feet (6.1 meters). The only metal element in such a system is the

1

horizontal aluminum channel that supports the plank at its top and bottom edges. The inner wall, separated by a three-foot (0.9-meter) air cavity housing blinds and light fixtures, consists of floor-to-ceiling translucent, acid-etched, UV-blocking laminated glass. Low-iron glass was used throughout to avoid the natural greenish tint of regular clear glass.

The Nelson-Atkins Museum of Art

1 Translucent channel glass curtain wall 2 View of inner wall with clear and acidetched glass 3 Exterior view of channel glass wall at night

2

3

201

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4 Partial elevation

5 Plan

202

203

A E B

J

D

C

12' (3.66 m)

The Nelson-Atkins Museum of Art

F

I

G

H

6 Section

A Sandblasted low-iron

F Light fixture

channel glass with translucent insulation

G Fireproofed

B Extruded-aluminum

stack joint anchored to steel tube C Laminated acid-etched

safety glass D Steel suspension rod E Galvanized-steel-

grate catwalk

steel beam H Automated blinds I

Concrete floor slab on metal deck

J Suspended ceiling

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7

7 Longitudinal section 8 Translucent glass lenses emerging from sculpture garden

8

The Nelson-Atkins Museum of Art

205

9

9 Exterior of glass lense 10 Daylit entrance lobby

10

Case Study

206

Case Study

207

The New York Times Building New York, NY United States

Curtain Wall Custom unit system with a frame of extruded-aluminum mullions supporting insulating glass and an external brisesoleil of horizontal ceramic rods Program Office space, ground-floor retail space, an open-air garden, and an auditorium Architects Renzo Piano Building Workshop; FXFOWLE Architects Client The New York Times Company Developer Forest City Ratner Companies Interior Architect Gensler Exterior Wall Consultant Heitman and Associates; Forst Consulting Company Structural Engineers Thornton Tomasetti MEP Engineer Flack and Kurtz Completion Date 2007

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208

In 2000, Renzo Piano won the competition to build the new headquarters of The New York Times Company. His design for the 1.5-million-square-foot (139,354-squaremeter), fifty-two-story tower features a custom-unit curtain wall system with floorto-ceiling insulating glass and a second layer of external sunshading ceramic rods. The building represents an application of the brise-soleil concept on an immense scale, unprecedented in New York City. The curtain wall incorporates ultraclear insulating glass in prefabricated units, framed by extruded-aluminum mullions that are anchored to the edge of each

floor slab. The vertical mullions, spaced on 5-foot (1.5-meter) centers, also support the external sun-shading veil of ceramic tubes—positioned about eighteen inches in front of the glass—which reduce solar heat gain by up to 50 percent. An innovative lighting system, developed in association with Lawrence Berkeley National Laboratory, takes advantage of the natural light coming through the curtain wall and uses automated dimming and shade systems to minimize the need for electric power, reducing energy consumption by 30 percent. In addition to providing critical sun-shading, the ceramic rods (186,000

1 Typical tower floor plan 2 West elevation at sunset

1

2

in all) create a unique diaphanous skin that defines the character of the building. The white rods reflect external environmental conditions, altering color with the changing sky—gray in overcast weather, bright white in midday sun, orange and pink as the sun rises and sets. During the building’s first year of use, the horizontal rods proved an irresistible invitation to three attention-seekers who scaled the curtain wall (two reached the top of the building using the ceramic rods like rungs in a ladder), prompting the owner to remove those closest to the base of the building in the summer of 2008.

The New York Times Building

209

3 Aluminum-framed glass curtain wall with external brise-soleil of ceramic rods 4 Interior view

3

4

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5 Partial elevation

5' (1.52 m)

6 Plan

The New York Times Building

211

3' 4" (1.02 m)

I

B

13' 9" (4.19 m)

A

J

E

C

F

D

G

H

7 Section

A Glazed ceramic tubes

with internal aluminum connection

F

Painted extrudedaluminum unit frame

G

Painted aluminum spandrel panel

H

Automated internal shade

I

Raised floor over concrete slab on deck

J

Suspended ceiling

B Painted aluminum

vertical strut C Painted aluminum

horizontal strut D Steel suspension rod E

Low-iron insulating glass with low-E coating

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212

The New York Times Building

8 Night view of tower

9

213

9 Ceramic-rod brise-soleil at main entrance

Case Study

214

Case Study

215

Spertus Institute of Jewish Studies Chicago, IL United States

Curtain Wall Custom hybrid system of structural, preglazed, silkscreened insulating glass units in multiple shapes mounted onto stick-built mullions of extruded aluminum Program Permanent and temporary exhibition galleries, classrooms, a library, an auditorium, conference rooms, a cafe, and a gift shop Architect Krueck + Sexton Architects Associate Architect VOA Associates Client Spertus Institute of Jewish Studies Curtain Wall Consultant Shepphird Associates Structural Engineer Tylk Gustafson Reckers Wilson Andrews MEP Engineer Environmental Systems Design Completion Date 2007

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The new Spertus Institute of Jewish Studies both contrasts with and complements the line of traditional masonry buildings it joins along Chicago’s famous Michigan Avenue, facing eastward toward Grant Park. Unapologetically contemporary, though respectful of contextual cues such as height and massing, the building’s main facade measures 80 by 181 feet (24.4 by 55.2 meters) and is clad entirely in a folded, faceted custom glass curtain wall. The effect of this crystalline structure is a combination of transparency and reflectivity, suggesting a sense of openness and connectivity that suits the institute’s mission. The curtain wall incorporates 726 individual pieces of glass in 556 different

shapes. Portions of the undulating wall project outward by as much as 5 feet (1.5 meters) and inward by 2 feet (0.6 meters). With such variation in orientation, the glass surfaces simultaneously transmit and reflect sunlight through and across the facade. The double-pane insulating glass includes a high-performance low-E coating on the second surface for improved thermal performance as well as a silkscreened pattern of white ceramic frit dots for solar shading covering 40 percent of the surface. Visible from within a few feet, the dot pattern disappears when viewed from greater distances and lends the glass a softness and material presence. The inner pane of the insulating-glass unit is laminated with a

1 Longitudinal section 2 View from Michigan Avenue

1 2

PVB interlayer, providing several benefits:

improved safety, better acoustical insulation, and protection from potentially damaging UV light. The glass is factory-glazed along each edge with a structural silicone sealant that adheres it to a minimal frame of extruded aluminum. These units are then mounted onto Y-shaped aluminum mullions, spanning vertically from floor to floor, that bend and twist as the shape of the wall dictates. Near the center of the facade, a portion of the wall peels away from the building mass to form a kind of canopy, sheltering the street-level entryway and revealing the construction method of the curtain wall.

Spertus Institute of Jewish Studies

217

3

3 Curtain wall extension forms canopy at entrance 4 Interior view of preglazed unit frame and Y-mullions 5 View toward Lake Michigan 4

5

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6 Partial elevation

4' 4" (1.32 m)

7 Plan

Spertus Institute of Jewish Studies

219

F

A G D

14' (4.27 m)

H

B

7' (2.13 m)

C

E

8 Section

A Structurally glazed

laminated insulating glass with low-E coating and ceramic frit silkscreen

E

Radiator

F

Concrete slab on metal deck

G

Fireproofed steel beam

H

Suspended ceiling

B Extruded-aluminum

unit frame C Bent extruded-

aluminum mullion D Adjustable translucent

blind

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9 Interior view

9

Spertus Institute of Jewish Studies

26 27

28

29

30

221

31

01

32

05

06

33

03

02

04

08

07

12

11

10

09

21

13

22 2 14

15

24 2 4 16

17

25 25 20

18

11

19

23 37 38

34

35

36

39

10

10 Diagram of curtain wall facets

Anchor plate Y-mullion

11 Curtain wall axonometric

Rotating knife plate extrusion Alum. saddle extrusion

12 Plan detail at typical Y-mullion

S.S. hook plate Alum. framing extrusion 1-7/16” laminated fritted low-iron glazing unit

Work point

12

Case Study

222

Case Study

223

United States Federal Building San Francisco, CA United States

Curtain Wall High-performance window wall with floorto-ceiling insulating glass, operable vents, and external sun-shading provided by a second skin of perforated stainless-steel panels at the southeast elevation and translucent glass fins at the northwest Program Office space for U.S. federal departments, including Labor, Defense, Health and Human Services, and Agriculture; health and fitness center; conference facilities; child care center; and a cafe Architect Morphosis Executive Architect Smith Group Client U.S. General Services Administration Curtain Wall Consultant Curtain Wall Design and Consulting Structural and MEP Engineer Ove Arup and Partners Civil Engineer Brian Kangas Foulk Natural Ventilation Modeling Lawrence Berkeley National Laboratory Artist Collaborators James Turrell, Ed Ruscha, Rupert Garcia, Hung Liu, Raymond Saunders, William Wiley Completion Date 2007

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The U.S. General Services Administration, acting as client for the new 600,000-squarefoot (55,741-square-meter) United States Federal Building in San Francisco, sought an exemplary building that would reduce consumption of natural resources, minimize waste, and create a healthy, productive workplace for the building’s daily users. The project team, headed by the architects of Morphosis, responded with a design featuring advanced sustainable technologies in an emphatically nontraditional wrapper. The building envelope is a machine that not only provides light, views, and protection from the elements, but also circulates air and reduces energy use. The main component of the complex is an eighteen-story tower conceived with a slender floor plate measuring 65 feet

(19.8 meters) wide, to maximize views and incoming light and to enable natural crossventilation of the offices, taking advantage of San Francisco’s temperate climate. The two broad faces of the tower are enclosed by walls of clear floor-to-ceiling insulating glass with operable windows. To protect these walls from excessive solar heat gain, sun-shading is provided at the southeast elevation by an external armature of perforated stainless-steel panels and, at the northwest elevation, by light-diffusing translucent glass fins. The articulation of these two shading systems, with the details of their fabrication and assembly clearly on display, defines the building’s character: a machine aesthetic that celebrates the importance of orientation and responsiveness to climate.

The building skin is not static. A centralized computer system automatically opens and closes windows and sunshade panels in response to interior air temperature and external environmental conditions, such as temperature, wind speed, and wind direction. (Manual override controls are also provided for use by individuals.) At night, the windows open to flush out heat that has built up during the day, allowing nighttime air to cool the building’s concrete interior. The thermal mass of the exposed concrete walls, columns, and ceilings keeps the interior cool throughout the day.

1 Interior view at office: aluminum-framed window wall with insulating glass, operable windows, and external sun-shading panels 2 Northwest elevation 3 Translucent glass fins at northwest elevation

1

United States Federal Building

2

3

225

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4 Partial elevation 7' 4" (2.24 m)

5 Plan

United States Federal Building

227

H D

I

A

13' (3.96 m)

B

E

G C F

6 Section

A

Perforated stainlesssteel sunshade panels

F

Operable outswinging windows

B

Galvanized-steel tube frame

G

Extruded-aluminum unit frame

C

Steel suspension rod

H

Radiator

D

Galvanized-steelgrate catwalk

I

Reinforcedconcrete slab

E

Insulating glass

J

Raised floor

J

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228

United States Federal Building

8

229

9

7 Perforated stainlesssteel skin at east corner 8 East corner 9 Oblique view from plaza 10 Perforated stainlesssteel sunshade in front of glass and aluminum window wall 10

Case Study

230

Case Study

231

Yale Sculpture Building New Haven, CT United States

Curtain Wall Standard stick system customized with an external brise-soleil, triple-pane insulating glass, and high-performance spandrel insulation Program Art studios, a gallery, machine shops, classrooms, and offices Architect KieranTimberlake Associates Client Yale University Structural Engineer CVM Engineers MEP and Civil Engineer BVH Integrated Services Environmental Consultant Atelier Ten Completion Date 2007

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In designing the new 51,000-squarefoot (4,738-square-meter) home for Yale University’s sculpture department, KieranTimberlake Associates was challenged to provide a high degree of transparency and natural light for the art studios while achieving ambitious overall energy-efficiency objectives, all within the context of New England’s harsh seasonal weather extremes. The building envelope plays a major role in the attainment of these goals, through the use of a high-performance curtain wall with innovative glass specification and solar design strategies. The Sculpture Building earned a LEED Platinum rating and was named one of 2008’s “Top Ten Green Projects” by the American Institute of Architects Committee on the Environment.

The curtain wall framing consists of standard stick-built mullions of thermally broken, extruded aluminum with external glazing caps. This system was customized through the use of high-performance glazing, including triple-pane, argon-filled, low-E coated insulating glass at vision areas; and on the exterior, superinsulated spandrel panels incorporating double-pane, low-E insulating glass, a 3-inch (7.6-centimeter) air space, and a translucent Kalwall fiberglass panel with aerogel insulation. The spandrel panels achieve an insulation value of R-20, while the average value of the curtain wall system overall is R-8— more than four times better than a conventional curtain wall. Due to the use of translucent spandrels, the entire curtain

wall transmits natural light, even though transparent glass is limited to vision areas (approximately 60 percent of the surface), and therefore, the need for artificial lighting is greatly reduced. The curtain wall also contains numerous operable windows for natural ventilation. The other important custom feature of the curtain wall is the array of horizontal aluminum sunshade louvers supported on vertical aluminum channels located approximately 2 feet (0.6 meters) outside of the curtain wall, on the south and east elevations. The angle of the louvers is calibrated to allow low-angle winter sun to reach the glass while blocking direct summer sun and guarding against excessive solar heat gain and glare.

1 East elevation at night

1

Yale Sculpture Building

233

2

2 Aluminum brise-soleil at southeast corner 3 Glass and aluminum curtain wall (left) and aluminum brise-soleil (right) 4 Interior view at sculpture studio

4

3

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5 Partial elevation 5' (1.52 m)

6 Plan

Yale Sculpture Building

235

A

H

I

8' 4" (2.54 m)

14' (4.27 m)

G

C

B

3' 11" (1.20 m)

F

7 Section

D

A Aluminum sunshade

E

F

Thermally broken extruded-aluminum mullion

G

Adjustable translucent blind

H

HVAC console

I

Aluminum bracket

J

Concrete slab on deck over structural steel framing

louvers B Vertical aluminum

channels C Triple-pane insulating

glass with low-E coating and argon fill D Double-pane

insulating glass with low-E coating E Translucent fiberglass

panel with aerogel insulation

J

Case Study

236

Case Study

237

The Cathedral of Christ the Light Oakland, CA United States

Curtain Wall Custom prefabricated unit system with laminated glass in extruded-aluminum framing mounted to a laminated-wood structural system. Program A cathedral, mausoleum, offices, library, conference center, cafe and bookstore, and underground parking Architect Skidmore, Owings and Merrill Architect of Record Kendall/Heaton Associates Client Diocese of Oakland Structural Engineer Skidmore, Owings and Merrill Mechanical Engineer Taylor Engineering Electrical Engineer Engineering Enterprise Completion Date 2008

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The Diocese of Oakland wanted its new cathedral to embody light, drawing on deep metaphoric associations in religious traditions. The cathedral complex, built to replace an older one that was damaged during the 1989 San Francisco Bay earthquake, includes a concrete base, housing offices, meeting spaces, residences for clergy, and a bookstore and cafe. Rising from the rooftop plaza of the base is the luminous main sanctuary, a tapered space measuring 100 feet (30.5 meters) in height, forming two interlocking spherical grids that are draped in glass and topped by a central glass oculus.

Within the sanctuary, which seats 1,350 people, the main building structure is composed of a series of curved and straight laminated Douglas fir columns that extend the full height of the building. The skin is formed by a custom curtain wall system, with unit frames of extruded aluminum holding 1,028 panes of laminated, low-E coated glass that are silkscreened with a custom-patterned ceramic frit. This effect renders the glass translucent, serving to diffuse the light passing through the curtain wall, and the glass walls glow at night when lit from within. Each glass unit measures 4.5 by 10 feet (1.4 by 3 meters). The curtain

wall is anchored to horizontal steel tubes that span between the massive upright wooden columns. At the top of the wall, vertical stainless-steel mullion extensions point toward the sky. The interior face of the enclosure is formed by wooden louvers that simultaneously diffuse and redirect sunlight to the interior, partially screen the curtain wall, and provide brief glimpses between louvers to create a sense of mystery as to the source of the light.

1 West elevation

1

The Cathedral of Christ the Light

239

3

2

2 Internal structure revealed by sunlight 3 Laminated glass with custom ceramic-frit pattern in unit frames of extruded aluminum 4 South elevation

4

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5 Partial elevation

4' 6" (1.37 m)

6 Plan

241

10' 2" (3.1 m)

The Cathedral of Christ the Light

A

B C

D

D E

F

H I G

7 Section

A

Laminated glass with low-E coating and custom-patterned ceramic frit

B

Extruded-aluminum unit frame

C

Horizontal steel tube

D Laminated Douglas

fir column E

Laminated Douglas fir sunshade louver

F

Steel rod cross-bracing

G

Reinforcedconcrete base

H

Light fixture

I

Maintenance walkway

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8

8 Ground-floor plan 9 Oculus at center of sanctuary ceiling with suspended aluminum panels to diffuse light

9

The Cathedral of Christ the Light

243

10

11

10 Detail of curtain wall connections at south elevation 11 Laminated wood structure and louvers at interior 12 Longitudinal section

12

Case Study

244

Case Study

245

100 Eleventh Avenue New York, NY United States

Curtain Wall Custom unit system with semireflective, low-E coated insulating glass set at various angles within aluminum and steel frames Program Residential condominiums Design Architect Ateliers Jean Nouvel Executive Architect Beyer Blinder Belle Architects and Planners Client West Chelsea Development Partners Curtain Wall Consultants CCA Facade Technology; UAD Group; Front Structural Engineer DeSimone Consulting Engineers MEP Engineer Atkinson Koven Feinberg Engineers Environmental Consultant Roux Associates LEED Consultant YRG Sustainability Consultants Completion Date 2009

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This twenty-three-story residential tower in Manhattan’s Chelsea neighborhood displays a dichotomy between front and back, solidity and lightness. The front of the building, facing west and south toward the nearby Hudson River, presents a patchwork of semireflective glass in curtain wall units of various shapes and sizes wrapping around a curved corner. What may be considered the back of the building, facing north and east, is outfitted in precastconcrete panels faced in black brick with smaller punched-window openings. From a distance, the glass curtain wall looks like a thin reflective membrane,

applied to the building in the direction of the major views; from a closer vantage point, it reveals itself as an intricate collage of angled glass panels set within an irregular network of narrow mullions. Insulating glass with a low-E coating and laminated inner pane (for safety and UV protection) is supported by extruded-aluminum frames, which are contained within larger prefabricated unit frames of powder-coated steel tubes. These steel frames, bolted to the edge of each floor slab, form megaunits, ranging from 11 to 16 feet (3.4 to 4.9 meters) tall and up to 37 feet (11.3 meters) wide, each holding numerous glass panels

tilted in different directions—left, right, up, and down. In all, there are more than 1,600 individually sized glass panels. This diversity of orientation results in striking optical effects. The glass wall oscillates between transparency and reflectivity, with no two adjacent glass panels the same. The irregular mullion spacing also serves to frame very specific views from within. Because of the curtain wall’s fractured imagery, the facade conveys a notion of individuality and specificity, resisting the tendency toward uniformity.

2

1 Rendering of west elevation 2 Reinforced-concrete structure under construction 1

100 Eleventh Avenue

247

3

3 Shifting reflections over the course of one day 4 Interior rendering of steel and aluminum curtain wall framing with angled insulating glass

4

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5 Partial elevation

17' (5.18 m)

6 Plan

249

C

F

B

E

A

12' (3.66 m)

100 Eleventh Avenue

D

7 Section

A

B

C

Laminated insulating glass with low-E coating Extruded-aluminum glazing adapter on steel tube unit frame Steel curtain wall anchor and fire-safe insulation at slab edge

D Extruded-aluminum

horizontal mullion E Adjustable shades F Finished floor

on reinforcedconcrete slab

Case Study

250

Case Study

251

166 Perry Street New York, NY United States

Curtain Wall Custom unit system featuring vertical and sloped low-E coated insulating glass supported in unit frames of extruded aluminum Program Residential condominiums Architect Asymptote Client Perry Street Development Corporation Facade Consultants Design phase: Front; Construction phase: Heitmann and Associates Structural Engineer Robert Silman Associates MEP Engineer Forum Engineering Energy Model Consultant Kinetix Completion Date 2009

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Sited next to Richard Meier’s iconic 173 and 176 Perry Street towers located near the Hudson River waterfront in Manhattan’s West Village, 166 Perry Street provides an alternate take on the glass-clad residential building. Here, the glass wall is not a continuously flat, vertical surface; the curtain wall angles variably inward and outward in vertically articulated bands. Due to the specification of a slightly reflective low-E coating on the glass and the angled positioning of the units, the curtain wall reflects both sky and ground conditions, changing

color throughout the day and presenting a collagelike assemblage of contextual imagery. The primary focus of the building envelope design is thus a celebration of access to light, air, and views—precious commodities in any Manhattan residence. Illustrative of the ongoing globalization of the facade industry, 166 Perry Street’s curtain wall units were assembled and tested in Shanghai, China, with finished prefabricated units then shipped to the construction site, where they were installed on premounted anchors at the edge of

1 Mock-up of curtain wall units 2 Installation of curtain wall units

1

2

each floor slab. The slabs cantilever beyond the structural frame, allowing for uninterrupted vision glass from floor to floor, without spandrel panels. The customdesigned unit frames consist of extrudedaluminum mullions, to which insulating glass is structurally glazed with silicone sealant. Out-swinging operable windows are provided within most of the curtain wall units for natural ventilation.

166 Perry Street

253

3 Rendering of faceted curtain wall units 4 Rendered exterior view at midday 5 Rendered exterior view at dusk

3

4

5

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254

6 Partial elevation

5' (1.52 m)

7 Plan

8' (2.44 m)

255

A

13' (3.96 m)

166 Perry Street

B

C

E

D

F

8 Section

A

Laminated insulating glass with low-E coating

B

Extruded-aluminum unit frame

C

Out-swinging operable window

D

Fire-safe insulation

E

Finished floor on concrete deck

F

Adjustable shade

Acknowledgments

The research that resulted in this book was supported by grants from the Graham Foundation for Advanced Studies in the Fine Arts and a Creative Research Award from the College of Fine and Applied Arts at the University of Illinois at Urbana-Champaign. I am grateful for the encouragement of colleagues in the School of Architecture at the University of Illinois, including Director David Chasco, Botond Bognar, and Jeff Poss. I am also thankful for the enthusiasm and insight of the numerous graduate students that participated in my curtain wall seminar at the University of Illinois over the past several years. And, while I’m at it, I will take this opportunity to thank a few teachers who were particularly important figures in my own architectural education: Sheila Kennedy, Leslie Gill, and Alejandro Lapunzina. Much of my knowledge of curtain walls in contemporary architecture was gained through years of professional practice and collaborative work with fellow architects and engineers. My time with the firm of R.A. Heintges & Associates, in New York City, was especially enlightening in this regard, due in large part to Robert Heintges, John Pachuta, Katherine Miller, Piergiorgio Pesarin, and Aulikki Sonntag, among many other important mentors and friends. This book is dedicated to Sharon and Ken Murray, with gratitude for a lifetime of encouragement and support. Scott Murray

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Illustration Credits

Frontmatter p. 2: photograph © Corinne Rose Part I p. 9, clockwise from top left: originally published in Architectural Record, JanuaryMarch, 1895, 305; photograph © Artists Rights Society (ARS), New York/ADAGP, Paris/FLC; Library of Congress, Prints & Photographs Division, HABS NY, 31-NEYO, 151-1; photograph © Scott Murray. Essay 1 1.1, originally published in Architectural Record, January–March, 1895, 305; 1.2, Library of Congress, Prints & Photographs Division, HABS ILL, 16-CHIG, 23-1; 1.3–1.4, photograph © Scott Murray; 1.5, Library of Congress, Prints & Photographs Division, HABS ILL, 16-CHIG, 66-1; 1.6, photograph © Chicago Architectural Photographing Company; 1.7, drawings by Jason Wheeler; 1.8, photograph © Scott Murray; 1.9, Library of Congress, Prints & Photographs Division, HABS ILL, 16-CHIG, 30-2; 1.10–1.12, drawings by Jason Wheeler; 1.13, photograph © Scott Murray; 1.14, drawings by Jason Wheeler; 1.15, Historic Architecture and Landscape Image Collection, Ryerson and Burnham Archives, The Art Institute of Chicago, Reproduction © The Art Institute of Chicago; 1.16, RIBA Library Photographs Collection; 1.17, RIBA Library Photographs Collection; 1.18, photograph © Botond Bognar; 1.19, Kansas Collection, Spencer Research Library, University of Kansas Libraries; 1.20, Library of Congress, Prints & Photographs Division, HABS CAL, 38SANFRA, 149-1; 1.21, drawing by Scott Murray; 1.22, photograph © Botond Bognar. Essay 2 2.1, © Artists Rights Society (ARS), New York/ ADAGP, Paris/FLC; 2.2–2.3, © Artists Rights Society (ARS), New York/VG Bild-Kunst, Bonn. Digital Image © The Museum of Modern Art/ Licensed by Scala/Art Resource, NY.

Essay 3 3.1, Library of Congress, Prints & Photographs Division, HABS NY, 31-NEYO, 151-1; 3.2, drawing by Jason Wheeler; 3.3, originally published in Architectural Forum, November 1950, reprinted courtesy of General Bronze; 3.4–3.5, drawings by Scott Murray; 3.6–3.7, photographs © Nelson Kon; 3.8, Library of Congress, Gottscho-Schleisner Collection; 3.9, drawing by Jason Wheeler; 3.10–3.11, drawings by Scott Murray; 3.12, photograph by Ezra Stoller © Esto; 3.13, drawing by Jason Wheeler; 3.14, Library of Congress, Gottscho-Schleisner Collection; 3.15–3.29, all drawings by Scott Murray, all photographs © Scott Murray; 3.30, RIBA Library Photographs Collection; 3.31, drawings by Jason Wheeler; 3.32, Library of Congress, Prints & Photographs Division, HABS MASS, 9-CAMB, 69-3; 3.33, photograph © Scott Murray; 3.34–3.35, photographs courtesy Perkins+Will; 3.36–3.37, drawings by Jason Wheeler; 3.38, photograph by Ezra Stoller © Esto; 3.39–3.40, photographs © Scott Murray. Essay 4 4.1–4.4, photographs © Scott Murray and drawing by Scott Murray; 4.5–4.6, photographs © Josh Wood; 4.7, photograph © Alastair Hunter/RIBA Library Photographs Collection; 4.8, photograph © John Donat/RIBA Library Photographs Collection; 4.9, photograph © Scott Murray; 4.10, drawings by Scott Murray; 4.11–4.12, photographs © Barbara Elliott Martin; 4.13–4.14, drawings by Jason Wheeler; 4.15–4.18, photographs © Scott Murray; 4.19, Library of Congress, Prints & Photographs Division, HABS WIS, 51-RACI, 5-6; 4.20–4.26, all photographs © Scott Murray and drawings by Scott Murray; 4.27–4.28, photographs © Botond Bognar.

Part II p. 65: both photographs © Scott Murray. Essay 5 5.1–5.3, photographs © Scott Murray; 5.4, drawing by Jason Wheeler; 5.5, photograph © Scott Murray; 5.6, drawing by Jason Wheeler; 5.7–5.15, all photographs © Scott Murray and all drawings by Scott Murray. Essay 6 6.1, diagram adapted by Scott Murray, from James Marston Fitch, American Building: The Environmental Forces That Shape It; 6.2–6.3, drawing and chart by Scott Murray; 6.4, image produced using THERM software from Lawrence Berkeley National Laboratory; 6.5, photograph © Scott Murray. Part III pp. 84–85: all images courtesy the architects. The New 42nd Street Studios p. 86, photograph © Scott Murray; p. 87, drawing courtesy Platt Byard Dovell White; figures 1– 2, courtesy the architects; 3–4, photographs © Scott Murray; 5–7, drawings by Scott Murray based on information provided by the architects; 8, courtesy the architects; 9–10, photographs © Scott Murray; 11, photograph © Dennis Gilbert/View/Esto. Melvin J. and Claire Levine Hall p. 94, photograph © Scott Murray; p. 95, drawing courtesy KieranTimberlake Associates; figures 1–2, photographs © Scott Murray; 3, photograph © KieranTimberlake Associates; 4, photograph © Scott Murray; 5, drawings courtesy the architects; 6–8, drawings by Scott Murray based on information provided by the architects.

Illustration Credits

263

One Omotesando p. 100, photograph © Botond Bognar; p. 101, drawing courtesy Kengo Kuma and Associates; figure 1, photograph © Kengo Kuma and Associates; 2, photograph © Botond Bognar; 3, drawings courtesy the architects; 4, photograph © Kengo Kuma and Associates; 5–7, drawings by Scott Murray based on information provided by the architects.

Terrence Donnelly Centre for Cellular and Biomolecular Research p. 132, photograph by Tom Arban; p. 132 and figure 1, drawings courtesy architectsAlliance and Behnisch Architekten; 2–5, photographs by Tom Arban; 6–8, drawings by Scott Murray based on information provided by the architects; 9, photograph by Tom Arban.

the architects.

William J. Clinton Presidential Center p. 106, photograph © Scott Murray; p. 107, drawing courtesy Polshek Partnership Architects; figures 1–2, courtesy the architects; 3–5, photographs © Scott Murray; 6–8, drawings by Scott Murray based on information provided by the architects. Green-Wood Mausoleum p. 112, photograph © Scott Murray; p. 113, drawing courtesy Platt Byard Dovell White; figures 1–3, photographs © Scott Murray; 4, drawing courtesy the architects; 5–7, drawings by Scott Murray based on information provided by the architects. LVMH Osaka p.118, photograph © Botond Bognar; p. 119 and figures 1–2, drawings courtesy Kengo Kuma and Associates; 3–4, photographs © Kengo Kuma and Associates; 5–7, drawings by Scott Murray based on information provided by the architect; 8, photograph © Kengo Kuma and Associates; 9–10, photographs © Botond Bognar. Seattle Public Library p. 126, photograph © Scott Murray; p. 127 and figures 1–2, drawing courtesy Office for Metropolitan Architects and LMN Architects; 3, photograph © Lara Swimmer/Esto; 4–6, photographs © Scott Murray; 7–9, drawings by Scott Murray based on information provided by the architects.

Torre Agbar p. 140, photograph © Dennis Gilbert/View/ Esto; p.141 and figure 1, drawings courtesy Ateliers Jean Nouvel; 2, photograph © Scott Murray; 3, diagram courtesy the architect; 4, photograph © Philippe Ruault; 5, photograph © Scott Murray; 6–8, drawings by Scott Murray based on information provided by the architects; 9, photograph © Philippe Ruault; 10, photograph © Scott Murray; 11, photograph © Hector Milla; 12, photograph © Scott Murray. Torre Cube p.148, photograph © Scott Murray; p.149 and figures 1–2, drawings courtesy Estudio Carme Pinós; 3–4, photographs © Scott Murray; 5, photographs © Estudio Carme Pinós; 6–8, drawings by Scott Murray based on information provided by the architects. Netherlands Institute for Sound and Vision p. 154, photograph © Scott Murray; p.155 and figure 1, drawings courtesy Neutelings Riedijk Architecten; 2–4, photographs © Scott Murray; 5–7, drawings by Scott Murray based on information provided by the architects; 8–10, photographs © Scott Murray. Skirkanich Hall p.162, photograph © Scott Murray; p.163 and figure 1, drawings courtesy Tod Williams Billie Tsien Architects; 2, photograph © Scott Murray; 3, photograph courtesy the architects; 4, photograph © Scott Murray; 5, photograph © Michael Moran; 6–8, drawings by Scott Murray based on information provided by

Trutec Building p.168, photograph © Corinne Rose; p.169 and figures 1–2, drawings courtesy Barkow Leibinger Architekten; 3, photograph © Amy Barkow/Barkow Photo; 4–6, drawings by Scott Murray based on information provided by the architects; 7, photograph © Corinne Rose; 8, photograph © Amy Barkow/Barkow Photo; 9, photograph © Corinne Rose; 10–11, photographs © Amy Barkow/Barkow Photo. Biomedical Science Research Building p. 176, photograph © Scott Murray; p. 177 and figure 1, drawings courtesy Polshek Partnership Architects; 2, photograph © Aislinn Weidele/ Polshek Partnership LLP; 3–4, photographs © Scott Murray; 5–7, drawings by Scott Murray based on information provided by the architects; 8, drawing courtesy the architects; 9, photograph © Scott Murray. ATLAS Building p.184, photograph © Scott Murray; p.185, drawing courtesy Rafael Viñoly Architects; figure 1, photograph © Scott Murray; 2, photograph © Luuk Kramer; 3–4, photographs © Scott Murray; 5–7, drawings by Scott Murray based on information provided by the architects.

Blue Tower p. 190, photograph © Scott Murray; p. 191 and figure 1, drawings courtesy Bernard Tschumi Architects; 2, photograph © Joseph O. Holmes; 3–4, photographs © Scott Murray; 5–7, drawings by Scott Murray based on information provided by the architects; 8, drawing courtesy the architects; 9, photograph © Nat Ward.

Illustration Credits

264

The Nelson-Atkins Museum of Art p. 198, photograph © Michael Robinson/Esto; p. 199, drawing courtesy Steven Holl Architects; figure 1, photograph © Scott Murray; 2–3, photographs © Steven Holl Architects, courtesy Chris McVoy; 4–6, drawings by Scott Murray based on information provided by the architects; 7, drawing courtesy the architects; 8–10, photographs © Scott Murray.

Yale Sculpture Building p. 230, photograph © Scott Murray; p. 231, drawing courtesy KieranTimberlake Associates; figures 1–2, photograph © Enzo Figueres; 3–4, photograph © Scott Murray; 5–7, drawings by Scott Murray based on information provided by the architects.

The New York Times Building p. 206, photograph © Scott Murray; p. 207 and figure 1, courtesy Renzo Piano Building Workshop and FXFOWLE Architects; 2, photograph © David Sundberg/Esto; 3, photograph © Scott Murray; 4, photograph © Nic Lehoux; 5–7, drawings by Scott Murray based on information provided by the architects; 8, photograph © David Sundberg/ Esto; 9, photograph © Scott Murray. Spertus Institute of Jewish Studies p. 214, photograph by William Zbaren © Krueck + Sexton Architects; p. 215 and figure 1, drawings by Krueck + Sexton Architects; 2, photograph by William Zbaren © Krueck + Sexton Architects; 3–5, photographs © Scott Murray; 6–8, drawings by Scott Murray based on information provided by the architects; 9, William Zbaren © Krueck + Sexton Architects; 10–12, courtesy the architects. United States Federal Building p. 222, photograph © Scott Murray; p. 223, drawing courtesy Morphosis; figure 1, photograph © Tim Griffith/Esto; 2–3, photographs © Scott Murray; 4–6, drawings by Scott Murray based on information provided by the architects; 7–9, photographs © Scott Murray; 10, photograph by Steve Proehl © Morphosis.

Cathedral of Christ the Light p. 236, photograph © Scott Murray; p. 237, drawing courtesy Skidmore, Owings and Merrill; figure 1–4, photograph © Scott Murray; 5–7, drawings by Scott Murray based on information provided by the architects; 8, drawing courtesy the architects; 9–11, photograph © Scott Murray; 12, rendering courtesy the architects. 100 Eleventh Avenue p. 244, image © dbox/Ateliers Jean Nouvel; p. 245, drawing courtesy Ateliers Jean Nouvel; figure 1, image © dbox/Ateliers Jean Nouvel; 2, photograph © Scott Murray; 3–4, image © Ateliers Jean Nouvel; 5–7, drawings by Scott Murray based on information provided by the architects. 166 Perry Street p. 250, image © ArchPartners/courtesy Asymptote; p. 254, drawing © Asymptote; figure 1, photograph © Asymptote; 2, photograph © Scott Murray; 3–5, image © ArchPartners/courtesy Asymptote; 6–8, drawings by Scott Murray based on information provided by the architects.