Preventing Defect Claims in Hot, Humid Climates

The following article was published in ASHRAE Journal, July 2008. ©Copyright 2008 American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. It is presented for educational purposes only. only. This article may not be copied and/or distributed electronically or in paper form without permission of ASHRAE.

Preventing Defect Claims In Hot, Humid Climates and T.. Brennan, By K.R. Grosskop Grosskopf, f, Ph.D.; P. P. Oppenheim, Oppenh eim, Ph.D., Ph. D., P.E., Member ASHRAE; and T Bren nan, Member ASHRAE

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nsurers paid approximately $200 million toward mold and moisture-related defect claims in 2000. That amount increased to $1 billion in 2001 and

$3 billion in 2003. During this time, premiums increased more than 50%, forcing one-third of all contractors to abandon work in markets where they could not obtain or afford liability coverage.* A confiden confidenti tial al survey was was ad adm mini nisstered in February February 2007 to attendees of the an annua nual Associ A ssociate ated General Contractors of America (AGC) Surety Bonding and Risk Man M anage agemen entt Conf Confere erence nce in L ong ongboa boat Ke K ey, Fl F la., to dete determine rmine whi which builldi bui ding ng el ements they thought were at greatest risk of defect claims. Respondents repre represented six six of the seven largest U.S. sureties, compri comprisi sing ng 45.6% of the $58.7 billion commercial liability market.1

Findings from participants who were involved in in more more than 17,000 17,000 combi combine ned totall cons tota constructi truction on defect claims claims indicat indicate e that 84% of claims are associated with moisture-related defects in building envelope systems (69%) and building mech echan aniical syste system ms (15%). (15%). More M ore than half (53%) of all defects are caused by faulty installation. Other causes of construction defect claims cited by  About the Authors respondents include design errors and K.R. Grosskopf, Ph.D.,  Ph.D.,  is assistant professor, omiissi om ssions ons (19%), im i mprope properr seque sequenci ncing ng and Paul Oppenheim, Oppenheim , Ph.D., P.E., P.E., is  is professor

*Krizan,

W., et al. 2003. “Mold lawsuits have industry feeling vulnerable as larger projects are eyed.” EngiW.,  neering News Record  Record  (ENR),  (ENR), 250(12).

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and oversi and rsight ght of trades (15%), defective materials (8%), inspections (3%), and otherr causes (2%). othe (2%). More M ore than 90% of respondents fel feltt the numbe berr of de deffect claims cl aims had increa increase sed d withi within n the las astt 10 years, with nearly half (48%) indicating that defect clai claim ms had increased more than tha n 25% 25% during during thi this peri riod. od. I n response response to the survey findings, findings, this article provides best practices to avoid HVAC and HVAC-related envelope claims in moisture-vulnerable cliimates. Am cl A mong the most vulne vul nerable rable of the these se are hot, humid cli climates, which which according to ASH ASHRA RA E arere regi gions ons tha thatt maintain either a 19.5°C (67°F) or higher wet-bulb temperature for 3,000 or more hours during during the warmest six six

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at the University of Florida, in Gainesville, Fla. Terry Brennan Brennan is  is principal scientist at Camroden  Associates in Westmoreland, Westmoreland, N.Y.

July 2008

Findings from participants who were involved in more than 17,000 combined comb ined total construction defect claims indicate that 84% of claims are associated with moisture-related defects in building envelope systems (69%) and building mechanical systems (15%). consecuti cutive ve months of the year, a 23°C 23°C (73°F (73°F)) or highe hi gher wetbulb bul b tempe perature rature for for 1,500 1,500 or more hours during duri ng the warmes rmestt six consecutive months of the year, or both. For the purposes of this discussion, a hot, humid climate encompasses all of Florida, the southern half of the Gulf-rim states between Flori orida da and Texas, and southeast coastal coastal Texas. Mechanical Defects

Roughly 3.6million(78.1 (78.1%) %) of all all U.S. commerci rcia al bu buiildings in 2006 2006 were air conditi conditione oned. Packaged units (36%), chil chi lled water systems (21%), (21%), and heat pump systems (17%) (17%) are the predomina nant nt ai airr-condi conditi tioni oning ng technol chnologies ogies used by U.S. com comm mercial buildings in the South (Figur e 1  ), although although theuseof these and an d other technol technologies ogies varies varies by market. market. Constructi Construction on def defects commonl only y associate associated with with these types of mechani nical cal systems incl nclude ude condensati tion on of outsi outside de or inte i nternal rnallly genera generate ted d water vapor within ducts, plenums, walls, and ceiling cavities caused by ina i nade dequate dehumidi dificati fication on and exhau exhaust st ventil ventilation. Condensation control consists of lowering the dew point of the indoor air bel below thedesi sign gn indoor air air temperature. Thi his s is is achieved by by dehum dehumidi diffyi ying ng return return and and venti ntillation air, air, exhausting si signifi gnificant cant sources of inte i nternal rnallly gene generate rated d moi oisture sture and, controll con trolliing the theinfiltration of ho hot, t, humid outside outside air. Ai Air that that is is at 90% relative relative humidi dity ty wil wi ll condenseon thefirst surface surfacetha thatt is 2°C 2°C (3°F) (3°F) cool coole er than than the the air. If If therelative humidity is i s 40%, 2 a surface must be 14°C (25°F) cooler.  Using the simplified Design ign Cri te teri ri a method of proposedA SH SHR RAE Stan Standa dard rd 160P 160P, Des for M oistu oisture re Control Control in Buil dings  , for buildings in hot, humid cliimates, users canmai cl ainta ntaiin indoor indoor RH of approxi roxim mately 60% (and no greater than 70%) at 24°C (75°F) while maintaining effective condensation control, as long as the relative humidity remains within within the lim li mits of occup occupan ant comf comfort and other appl appliTher mal cable standards (e.g., ANSI SI/A /ASH SHRA RAE E Standard Standard 55 55,, Ther Envii ronme Env ronmental ntal Conditi ons for for Human Occupancy  Occupancy  ).  To  T o achieve effectiv ive e dehumid idifi ific catio ion n, HV HVAC sy systems are designed to provide a suitable fraction of sensible and latent capaci city ty to maintai aintain n desirable indoor i ndoor temperature and and humidity levels based on the climate, building type, building use, and num numbe berr of occupan occupants. ts. Moi M oisture sture removed from from the ai airr must be rem removed from from the buildi ding. ng. Conde Condensate that is i s not promptly promptl y drained drained out of the mechani nical cal system may overflow drain drai n pans, lea leak from from condensate drai drain n li lines to surrounding surrounding moi oisture-vul sture-vulne nerable rable materi rials, als, or be entrai ntraine ned back into i nto the supply air (Photos 1a and 1b  ). Stagnant condensate al ). also so can provide a breeding ground for viruses, bacteria and fungi. July 2008

ASH SHRA RAE E pre prescri scribe bes a dra draiin pan pan sl slope ope of 1 cm/m (0.125 (0.125 in./ in./ ft) to an outl tlet et at the lowest lowest point point and theuseof PP-traps traps on the the nega gati tive ve (suction) (suction) side si de of dra draww-through through systems to prevent hot, humid air from being drawn into into the air ha handl ndler er through the condensate drain. drain. In additi ddition on to eff ffe ecti ctive ve dehumidi dification, fication, desi design consi side deration must begiven to exhau exhausti sting ng inte internal source sources s of humidi dity ty.. Man M any internal sources of moisture, such as indoor swimming pools, spas, ki kitche tchens, ns, and bathrooms throoms,, req requi uire re exhau exhaust st venti ventillatio ation. n. Building occupants are another significant source of internally nall ygeneratedmoi oisture. sture.Hum Humansareapproxim approximately60%water by weight and consume roughly 2 L (0. (0.5 5 gallon) of water per day. Exhaled breath and persp perspiirati ration on relea release roughly 1.4 kg kg (3 lb) l b) of water vapor per person per per day to theindoor air. air. In additi ddition on to wate terr vapor, vapor, chemical and biol ological ogical contaminates in in the indoor indoor air air al also so must be removed. The The requi uirem rements for outsi outside air venti tillati tion on for commerci rcia al bu buiildings in the U.S. arepro provi vide ded by ANSI ANSI/A /ASH SHRA RAE E Sta Stand nda ard 62.1-2004, Ventilation for Acceptab Acceptable le I ndoo ndoorr Ai r Quali ty ty,, and are defined by buil buildi ding ng use. The The quanti ntity ty of outside air can vary from from 15 cfm (7 L/s) L /s) per person in in a typical typical of office fice envi vironme ronment, to as much as 100% fres resh h air ventil ventilat atiion in speci ciali alized zed healthalth-care care units. In I n hot, hot, humid cli climates, the quantity of outs outsiide venti ntillation air should, at a mini nim mum, exceed the quantity of exhaust air air to mai aintain ntain posiitive bui pos builldi ding ngpressuri rization. zation. Withou Without posi positi tive vepressuri rization, zation, humid air wi willl readi dilly ente enterr through door door and window openi nings ngs or infil infiltrate trate through the envelo velope pe. Al Although the bui builldi ding ng may be desi signe gned with with positive positi ve pressu ssuri rization, zation, an unba unbalance ced d HVA HVAC C systemmay induce inducenegati tive ve air pressurein parts of thebui builldi ding. ng. Subsequentl ntly, y, suppl ply y andreturn air in each roomof thebui builldi ding ng must bebalancedto minim minimize theinfil nfiltration tration of hot, humid air. Howeve ver, r, venti ventillation air air in in hot, humid cli climates is is another potenti ntial al source of moisture in buil buildi dings. ngs. Depen Dependi ding ng on the quantity of outside air ventilation, dedicated dehumidification ti on systems (e.g., (e.g., energy recovery ve venti ntillators, desi desiccants ccants, or enthalpy wheels) may be necessary. I n cases where the ai airrconditioni conditi oning ng system alone can be used for for effective effective dehumidi di-fication, ficati on, energyrgy-effi effici cien ent reheat strategi gies es(e.g. (e.g.,, energy recovery exchangers, hothot-ga gass-bypa bypass, runa runaround coil coils, or heat pipe pipes) may beconsi considere dered to mai aintai ntain n adequatedehumidi dificati fication on when tim timeof--day or seasonal sensibl of ble eloadsarelow, and, to avoid providi provi ding ng supply sup ply air that is is lowe lower than the dew point point of the indoor indoor ai air. In In addition, CO CO2 sensors can beused to match fresh freshai airr ventil ventilati ation on to actual buil buildi ding ng occupancy inste instead of maximum desi sign gn occupancy in in buil buildi dings ngs where humans are thedominant source of ASHRAE Journal

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internal rnallly generated moisture and indoor indoor Other 1% Other 3% air pollution. Central AC Central AC Common defects related to HVAC 13% 14% Packaged Units Packaged Units design in hot, humid climates include Heat Pumps Heat Pumps 38% 36% 11% 17% inadequate de dehum humidi dificati fication on caused by Individual oversi ove rsized zed sensi nsibl ble e capaci pacity ty and reduced reduced Individual Units 16% Chilled Water Chilled Water Units 12% airflow (especially during seasonal or 21% 18% time-of-day part-load conditions), inadequa quate te exhaust exhaust for for interna nternall sources of moi oistu sture, re, and and insufficie insuffici ent ventil ntilat atiion South U.S. air to maintain positive building air pressure. Common construction (e.g., Fi gure 1: Pr ed edominant ominant cooling equipment in U.S. comme commercial rcial buildi ngs by pe percentag rcentage e of installation) defects include duct leaks, to 3  tota tall fl oorr ar ea. oo poor bal balan anci cing ng on mul ulti tipl ple e inle inl et exhau exhaust st systems, closed or malfunctioning exhaust dampers, and exhaust air vented to an unconditioned space within the building ins nste tead ad of of outd outdoors oors (e.g., via vi a a ce ceiling cavi vity). ty). Method thods s to promote and maintain effective building dehumidification in hot, humid climates include: Sizi Si zing ng the cool cooliing system to meet, but not exceed, the sensi nsibl ble e desi sign gn load oad;; Providing staged cooling capacity so that a fraction of the capaci pacity ty can be operated when sensibl ble e loads loads are too low for effective dehumidification; Maintaining positive internal air pressure; Provi Pr ovidi ding ngaddeddehumidi dificati fication on usi using ngenerg ergyy-effici efficien ent reheat strate strategi gies; es; Providing Provi ding dedicate dedicated dehu hum midifi difica cati tion on for for venti ventillati tion on air; Using CO2 sensors to match Standard 62.1-2004 62.1-2004 outdoor venti tillation req requi uirem rements to actual occupancy inste instead of maxi axim mum desi esign gn occupancy; and Using enthalpy sensors if conditioning or precooling with outside air. Condensati tion on control also incl i nclude udes insu insullating equi uipm pment surfaces and materi rial als s that wil will unavoi voidab dably condensewater vapor, such as chilled water pipes, valves and fittings, air-handling cabinetsandsupply ductspassi ssing ngthroughunconditi tione onedspaces (Photo 2  ). Closed-cell insulation should be used where practi). call to provide a the ca thermal buff buffe er and an ai air infil i nfiltration tration barri barrie er. Expos xpose ed interior HVA HVAC C surfac surface es that thatwi willl unavoi voida dably come comein contact with with condensatemust befabri abricate cated from from hardrd-surf surface aced materi rials als such as as galvanizedmetal, andin certai rtain n appli applications, cations, stainles stainl ess steel. The These se materi rials als must be resi resistan stant to corrosi corrosion on and an d mold growth and easil asily y clea cl eaned. Methods to promote promote and maintai aintain n effective effective buildi buil ding ng condenPhot os 1a and 1b: Con densate pan overfl overfl ow in to r etur n ai r pl enum sation control in hot, humid climates include: caused d by blockage of condensate drai n l in e. Sealing and testing all ductwork, plenums, and air cause 4 ,5 handl ha ndle ers; Avoiding use of rooms, crawl spaces, stud wall cavities, I nst nstall alliing wate water piping piping in in inte interi rior or wal walls and chases to or other unsea unsealedbui builldi ding ng cavi viti ties esas return air air plen plenums avoi void d condensation. condensation. (Photo 3  ); ); Care should should be taken to ensure the mechani chanical cal system is not Ins nsulati ulating ng all chil chillled wate terr piping, piping, ductwo ductwork, rk, and ai air-han r-han-- a source of unwanted moi oisture sture or water penetrati netration on into into the dling equipment (especially in unconditioned spaces); buildi buil ding ng.. Li L ikely sources sourcesof rainwater penetration include includeroof rooftop top Ins nsta tallling air handlers, chill chil led wate terr piping piping and ductwo ductwork rk penetrati trations ons (e.g., (e.g., curbi curbing ng around packaged units units and exhaust inside the building insulation and air barrier; and fans) and wall penetrati trations ons (e.g., ventilati ventil ation on intake intakeand exhaust •

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Photo 2: Condensation Condensation on an u nin sulated chill ed water water l in e in an un condit ion ed

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air louve air louvers) rs).. To prevent moi oisture sture probl roblem ems causedby blown rain rain enteri tering ng outdoor air air intake intakes, conside consider using using louve louvers that meet AMCA 500-L-99, Laborator y Methods M ethods of Tes Testi ti ng Louve L ouvers rs for  for or inta intake air velociti veloci tie es le less than500fpm(2.5 m/s). Rating, f  The  Th e permanent HVAC HVAC sys system may  be   be used for interior space conditioning and dehumidification during construction

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Photo 3: M old growth i n a wall cavity depres depress sur ize ized d by a return plenum.2 

only if   operating the systemdoes not void  operating voi d the manu anuffacturer’s

warranty and, if all return air locations are protected from contam conta mina nati tion on by providi providing ng adeq adequa uate te filtrati filtration on at each return air loca l ocati tion on in in add addiiti tion on to filtrat filtratiion at at theret return urn ai air side sideof the coills. Ai coi Air hand handllers, coil coils, drai drain pans ns,, filte fil ters, rs, humidifi difie ers, hea heat exchange xchangers, rs, and mixed air plenu pl enum ms should should be desi signe gned d and

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installed according to Standard 62.1Other 2%  Window Glass  Window Glass Siding Siding 2004 to be easily inspected, maintained, 1% 2% 6% 5% and cleaned. Specific attention should Metal Panels Metal Panels 12% 15% be given to the inspection of the folConcrete Panels Concrete Panels lowing mechanical components during Brick, Stone, or Stucco Brick, Stone, or Stucco 10% 12% 50% 51% installation: Concrete Block  Concrete Block  Drain Drai npans, pans,drain drainpan panoutlet outlets, s,trap traps, 17% 17% and an d disposal. disposal. Insulati nsulation on and and vapor re retarders on expose xposed d surface surfaces expected to fall fall South U.S. bellow the dew point be poi nt of ambi bie ent air (e.g., chilled water lines, re- Fi gur e 2: Predomin ant exterior wall systems systems in U .S. comme commerci rci al bui ldi ngs by perce percentage ntage frige fri gera rant nt line li nes, air condi conditi tion oniing air of to 3  tota tall fl oor ar ea. handlers, and chillers) particularly Testt M ethod for D ete eterr mini ng at transitions (e.g., penetrations through walls, floors to ASTM E779-03, Standar d Tes and an d ceili ceil ings, support clam cl amps, valves valves, da dam mpers, pumps, Ai r Leakage Rate by Fan Pressuri Pressuri zation (blower door test), blowe bl owers, and gages) s).. and an d duct duct seal tightn ti ghtnes ess s accordi according ng to A ST STM M E 1554-03, Test eterr mining External Air Leak Leakage age of Air Air Di str i-  Access panels (e.g., air air handlers, handlers, filte fil ters, coil coils, drain pans, Methods for D ete Systems ms by Fan Pr es essuri suri zation  andsuppl supply y ducts near air air handlers) handlers) to ensure that they al- buti on Syste  (low-rise residential and  (low-rise low inspe inspecti ction on and and maintenance of HVA VAC C components. small low-ri ow-rise secommerci rcia al bu buiildings). Di Diag agram rams lab labe eling key Exha Ex haust ventil ntilat atiion systems, for for duct seali aling ng,, insu i nsullat atiion, components and operating instructions should be affixed to and an d vapor control. control . the mech echanical anical systemto aid aid others others in i n accessi ssing ng and and repairi ring ng During Duri ng bui buildi ding ng startrt-up, up, an inde independent, certified certified commis- the HVAC system. This may include diagrams of flow direcsioni si oning ng agen agentt should should ensure ensure encl nclosure osure ai airti rtightn ghtnes ess s according according tions and valve locations and functions in the commissioning documents (e.g., as-built drawings), as well as information on HVAC operations and maintenance activities, personnel, and contractors. •

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Envelope Defects A s shown shownin Figur e 2  , exterior insulation and finish system

Adverti se seme ment nt for me merl rl y in thi t his s space space..

(EI FS) (EI S),, stucco and and brick brick veneer are are thepred predom omiina nant nt wal wall systems used by U.S. commercial buildings in the South (50%) fol olllowed by concrete pan panel els s and and masonry units units (29%) and integrated metal glazing (15%). Construction defects commonl only y associ associate ated with with thesetypesof wall systems incl include uderai rain n and groundwater penetration, capillary action (e.g., wicking), water wa ter vapor vapor infil i nfiltrati tration, on, and subse subsequent condensa nsati tion. on. In I n hot, humid cli climates, air air infil i nfiltrati tration on ma may be the domina nant nt source of moi oistu sture re in in air-cond air-condiiti tione oned bui buildi ding ngs. s. Me M ethod thods s to preve prevent nt water vapor migrati migration on and subsequent condensati condensation on insi inside de wall cavities and building interiors include: I nst nstall alliing mat ate eri rials als with with low vapor permeability to the warm si side of the the therm thermal layer; Selecting wall insulation that meets ANSI/ASHRAE/ Energy rgy Standard Standard for Bui ld-  I ES ESNA NA Stan Standa dard 90.1-200 90.1-2004, 4, Ene i ngs Exce Except pt L ow-Rise Re Res si den denti ti al Bui ldi ngs ngs,, for the climate; and Designing walls to dry to the interior, exterior, or both.  The  Th e wall assembly illu illus strated in Figur e 3   shows an  sho an EIFS EI FS on metal framing with with a properl rly y designed drai draina nage ge pl plan ane, e, vapor vapor retarder, air ba barr rriier er,, and thermal envelope appropri appropriate atefor hot, humid cli climates. The assembl bly y hasaconti continuous nuous drainage drainagepl plane ane provi pro vide ded by bui building wrap insta installed on theinside of thestu stucco cco renderi rend ering ng that that is i s draine drained to the exteri rior. or. An A n air air gap betwe between the exteri xterior or rigi ri gid d insulati insulation on and and the drai drainag nage plan ane e provi rovide ded •

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by a spacer mat, mat, channels, or textured bui buildi ding ng wrap provide provides s a cap capillary break and all allows ows liqu quiid wate terr to drai drain. In In additi ddition, on, the drainage drainagespaceprovi provides des avented or flowflow-through through assembl bly y that al alllows dry ryiing to the outsi outside de. L atex paint paint on the interior interior gypsum board provides a semipermeable, Class ClassIII vapor retarder (≤ 10 perms) that that resists resists the exfil xfiltra trati tion on of ins i nsiideair into i nto the thewall cavi vity ty whi while allow owiing the the walll to dry to the wa the interi rior or if if wette tted. d. An air barri rrie er is is provi vide ded by the interior interi or gypsum board, the the exteri xterior or stucco ren rende deri ring, ng, the 6 exterior sheathing or theexteri xterior or buil buildi ding ng wrap.  Ma M ateri ria als with with low vapor permeab abiility, in this this case the ri rigi gid d pol polystyrene ystyrene, are installed on the outside of the primary (batt) insulation layer to avoid condensation condensation withi wi thin n the wall ca cavi vity. ty. Together, these elements resist resist the entry of of water vapor into i nto thewall cavi vity ty and ensurethetemperatureof condensi nsing ngor moi oisture-accum sture-accumul ulati ating ng surface surf aces remai ain n above the dew point point of the infiltrati infil trating ng or exfiltra fil trating ting air. Special desi sign gn considerati ration on must also begiven to brick brick and masonryry-cl clad adwall walls s to prevent therai rain-sunn-sun-dri driven venwater vapor dynam dyna mic. If I f the cl clad addi ding ng is brick bri ck or concrete mason asonry ry and the wall is insulated with high permeability (>10 perm) porous insulati nsulation, on,theclad claddi ding ngshouldbebackck-ven vented, an and dlow lowperme permeabiliity (< abil (