Natural Light in Learning Environments

University of Nicosia Department of Architecture Thesis: ARCH-541

Natural light in learning environments

Student: Michaelidou Katerina

Supervisors: Xenopoulos Solon Patsavos Nicholaos

January 2012

Contents

Abstract …......................................................................................................................................... 1

Introduction…......................................................................................................................................2

1.

History of Daylight use in Learning environment....................................................................... 4

2.

Natural Light and health …....................................................................................................... 6

2.1 Circadian rhythms …................................................................................................................. 8 2.2 Seasonal affective disorders and depression …....................................................................... 10 2.3 Daylight and stress …............................................................................................................... 11 2.4 Natural light, learning performance and health ….................................................................... 11

3. Health and the contribution of views through windows …....................................................... 13 3.1 Building environments rich in nature views …........................................................................ 14 . 4. The quantity of daylight and the users visual comfort

…........................................................ 16

4.1 Light and the task …................................................................................................................ 17 4.2 Minimum acceptable levels of illumination for schools

….................................................... 18

4.3 When daylight is too much? …................................................................................................ 19 4.4 Glare

…................................................................................................................................... 19

4.5 Central and peripheral vision …............................................................................................... 21 4.6 Brightness adaptation …........................................................................................................... 22

5. Light on materials and surfaces …........................................................................................... 24 5.1 Diffusing and specular materials …......................................................................................... 26

6. Daylight design in learning environments and the relation with the space ................................ 29 6.1 Natural light affecting and defining a space …........................................................................ 31 6.2 Natural light connecting interior spaces ….............................................................................. 33

7. Approaches and daylighting systems for optimum quality and quantity of natural light in learning environments …............................................................................................................... 36 7.1 Daylighting systems …............................................................................................................ 37 7.2 Case studies …......................................................................................................................... 45

Conclusion

…................................................................................................................................ 54

Bibliography: …............................................................................................................................. 55

Acknowledgement This thesis project would not have been possible without the support of many people. I am heartily thankful to my supervisors Solon Xenopoulos and Nicholaos Patsavos, and to my professors Petros Lapithis, Anna Papadopoulou and Michail Georgiou whose encouragement, guidance and support , enabled me to develop an understanding of the subject. Lastly, I am grateful for the support I received from my family.

Abstract

The aim of this research is to investigate and explore the importance of architectural elements in relation with the learning environment, focusing on natural light. The research will try to determine the positive effects of taking advantage of natural light in the architectural design of learning environments. More specifically it will study the positive effects that are connected with students performance, health, the aesthetic and efficient quality of space and the possibilities that arise from the implementation of natural light in a learning environment. These positive effects are connected with better quality of learning which is human-centered and sensitive towards the environment. This approach can be seen as a necessity rather than a luxury, especially in the days that education is considered essential. In effect will lead to conscientious individuals and stronger societies able to confront today’s and tomorrow's challenges. Further more the research will provide ways in which architectural design can use natural light as well as other methods that are connected with the implementation of natural light, in order to create high performance learning environments.

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Introduction

Learning environments and especially schools have always been of great interest for architects mainly because through design those spaces can influence a child’s education and future. A school is not just a building to accommodate students and teachers, and it must not be seen as such. Architects and scientists named school environments as the ''3rd teacher'', and this is because the learning environment can play an important and significant role in students learning and academic performance. Taking for instance the nucleus of a school which is the classroom it can be seen that in an every day basis a student must do certain activities in the classroom, like reading, writing, drawing, solve mathematical problems, that are directly connected with the environment in which they perform. The learning environment if designed with consideration can be one of the most important components for successful learning and teaching. And although many would claim that a good teacher can teach anywhere and pass successfully the knowledge to students, research, based on how the built environment affects learning suggests that space, is equally significant. When an architect is asked to design a school there are several aspects that have to be taken into account. The academic program of the school and the activities that will take place in order to justify the facilities and the usage of each room, the number of students in order to justify the size of the school, the limit of permitted cost etc. In order to achieve the quality of learning environment the architect must be able through the architectural design, to create the best possible space for the users. Components such as air quality, materials, thermal performance, school, class size's, views, circulation and lighting of spaces are very important in order to create an environment which will be pleasant and helpful for students and teachers and it will not just be a building which only accommodates them.

This research will concentrate on the importance of natural light in a learning environment. While dealing with natural light in a learning environment the architect will come across many other aspects like natural ventilation, views, the relationship of the classroom to the outdoor spaces, the orientation of building and classrooms, the colors and materials in the space that will have to be chosen in order to improve the quality of the natural light without causing discomfort or other negative effects. Moreover the design has to deal with aspects such as heat gain and loss and shading when necessary to control the amount of light in the space.

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Chapter 1 presents briefly the history of daylight use in learning environments. Chapter 2 describes how natural light affects humans health and their learning performance and in chapter 3 how views, that is a component when having windows in a learning space, affect the users health and their academic performance. Chapter 4 is about the quantity of daylight in a learning environment and the users visual comfort. It presents the connection of light in a space with the tasks that are performed, the minimum acceptable conditions for desk-based work spaces such as schools, what is glare and when daylight in a learning space is too much. Moreover, this chapter contains information about the central and peripheral vision and the brightness adaptation of humans. Chapter 5 describes how natural light reacts on materials and surfaces and chapter 6 presents the interrelationship between light design and the spaces of a leaning environment. Moreover, it describes how natural light can be used to define a space and how it can be used to connect interior spaces of a learning environment. Chapter 7 describes several approaches to achieve optimum quality and quantity of natural light in a learning environment. Presents the two general categories of daylighting systems for learning environment and case studies of schools that use several daylight strategies and systems to achieve successful illumination of their facilities with natural light but also energy-efficiency.

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1 . History of Daylight Use in Learning Environments

In 1874, Robson suggested in the book, School architecture:practical remarks on the planning, designing, building, and furnishing of schoolhouses that day-lighting of classrooms was merely important. He further suggested use of day-lighting through sunny windows or sourced from the north, and that south or south-west lighting should be avoided. This was widely implemented in United Kingdom schools. Robson further advised that the classroom is well lighted when it has about 20% glazed area to floor areas. And is worth mentioning that glare at this early period was already avoided. From the 1900s to 1930s, there had been emphasis on the use of daylight in schools. This was called the ''open air school'' and it was achieved with a complete opening to one side of the classroom with a garden site. This approach also achieved good ventilation of the classroom and also the facilitation of sunlight penetration into the classroom. 1

The open air school was so popular that persisted until after the Second World War. An innovation that was adopted at that time was the maximum use of glazing area. Daylight was retained as the principal source of lighting. By 1984, glare from large windows as well as heating of classrooms during summer had policy-makers in the education sector reconsider the design where artificial lighting was introduced in classrooms. The introduction of fluorescent lights as well as airconditioning reduced the sizes of windows in classrooms and in addition, educators found windows to distract students attention in class.

During the oil crisis in the 1970s, windowless schools in the US started to be a common phenomenon and at some States the authorities even passed a law requiring all schools to be windowless and air-conditioned.

Afterwords through research, windowless classrooms or

windowless boxes had been found to have a negative effect on learners such as being prone to complain, show decreasing confidence and increasing absences and moreover it has been found that the majority of students preferred to sit or work near windows because of the daylight. 2 By 1992, daylight impact on learning and the school environment has been associated to improved performance. It was suggested that “work in classrooms without daylight may upset the basic hormone pattern, and this in turn may influence the children’s ability to concentrate or cooperate, and also eventually have an impact on annual body growth and sick leave. ”3

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References: - 1: Clay F. Modern school buildings. London: Batsford , 1929.

- 2: United States Department of Energy. National Best Practices Manual for Building High Performance Schools , 2010

- 3: Kuller R, Lindsten C. Health and behaviour of children in classroom with and without windows. Journal Environmental Psychology , 1992 .

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2. Natural light and health

Humans are strongly connected with natural light, sometimes consciously and sometimes not. The human body is connected with the diurnal cycle of light and dark and also is tuned to the spectrum of the suns radiation. Even if people are not aware of in some cases they respond to natural light and this can affect them with a variety of ways.

Daylight or natural light can affect people's health, interaction with other people, psychology, mood, and the ability to carry out visual tasks. Obviously if natural light affects people in that extend it certainly affects their learning abilities, performance, concentration, health and psychology in all aspects of their lives and certainly affects students in academic performance.

The electromagnetic radiation from natural light, coming directly from the sun, can harm but also benefit the human body. Therefore, exposure to direct sunlight must be controlled. Although direct sunlight is valuable for health the over exposure can prove harmful, for that reason, there is a necessity to keep a balance and avoid overexposure and underexposure to direct sunlight. The natural light even if its not direct to the body can affect positively the maintenance of mental and physical health. 1

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Children and students spend most of their time during the day period in schools and learning environments. Therefore is merely important for their mental and psychological health and as a continuation for their learning abilities and progress the school facilities to provide them with the maximum optimum quality and quantity of natural light. This is a conclusion that arises from several researches and experiments on the field of how and at what extend the educational facilities affect students. This paper will show several researches and experiments in the next chapter on how natural light affects mental and physical health and how it connects with students learning outcomes.

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2.1 Circadian rhythms

“The human body uses the natural circle of light and darkness during the 24 hour period of day to regulate it's daily sequence of changes of sleep, hanger, body temperature, alertness and most hormone production”2 necessary for the organism to function. Those everyday necessary changes for humans and mammals are controlled by the circadian rhythm. “Disturbing them gives the symptoms of jet lag, shift-work and of sleep disorders .” 3 Lack of daily exposure to light is one of the most important factors that can disturb that natural circle of the body. This is happening because in the human body there are various circadian rhythms that are interlinked and together have an inherent cycle time of approximately 24 hours. These cycles are modified and affected by external stimuli like the exposure to light. 4

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Research on that field has shown that the correct function of circadian rhythms release amongst other hormones, hormones that are responsible for the improvement of the “immediate memory between ten and twelve o’clock in the morning time” 5, therefore contributes as a positive factor in the learning procedure of students during the school hours. From six in the evening to midnight the hormones that are released are responsible for the “long term memory being at its best so there is a better window of time for studying school work.” 6

The correct function of the circadian rhythms is more important to children since their system seems to be more sensitive to this hormonal variation. Proper daylight design for classrooms and school facilities is crucial for the proper function and continuation of the bodies natural clock, and equally important for the learning performance of students.

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2.2 Seasonal affective disorders and depression

Seasonal affective disorder is one of the side effects of lack of daylight. “It is considered as a depressive illness that varies with the time of year.”

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It more often occurs during winter periods

and less often during the summer periods. The symptoms of SAD are common to other types of mental depression illnesses. “Over sleeping, mood changes, lack of energy and over eating” 8, are the symptoms of SAD in winter. “The opposite occurs for SAD during summer period, lack of sleep, loss of appetite and weight loss.”

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What is very important and directly connected with

children-students is that SAD occurs mainly in young adults and children and less in middle age and old people. This disorder can cause depression, lack of concentration and fatigue among other of it's many symptoms. Similar symptoms such as restlessness, being prone to illness and irritability were discovered in children spending the school days in windowless classrooms. Children in day-lit classrooms developed higher concentration skills and showed none of the negative symptoms.

A common hypothesis of many studies is that a brain hormone called

melatonin is inhibited by light. This hormone tells to the body when its time to wake up or when to go to sleep. Melatonin is believed to be the main hormone affecting seasonal affective disorder. The rate of release of this hormone is controlled by the illumination of the environment. Daylight illumination is of more significance to the health of children since the levels of this hormone seems to fluctuate more than in adults. 10

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2.3 Daylight and stress

Another hormone associated with the presence of daylight is Cortisol. High levels of Cortisol during the day and low levels during the night follows the circadian rhythm. High amounts of this hormone can decline sociability, medium levels seem to promote concentration and increased focus, according to a Swedish investigation of 90 elementary school students. Too much or too little of this hormone influences children ability to concentrate and affects their growth. It is very clear that daylight has a measurable effect on health in adults and especially children. Most of these effects are dependant and interrelated to each other, all controlled by daylight. The growth and development of children is very important, the large amount of time spent in school directly points to the need for these facilities to be designed for their health and well-being. Especially in a country like Cyprus which has many sunny days during the year in comparison with other countries. A facility properly designed will have fewer absences and more productive days than one that is ill-fitted for education. 11

2.4 Natural light, learning performance and health

As mentioned above, health, mood and learning performance is strongly connected with daylight. Many studies have confirmed the positive relationship between daylight and learning enhancement. In various studies conducted, it was found that lighting consistently impacts on the health, behavior and achievement of students in an indoor learning environment. The Heschong Mahone Group examined the math and reading scores of students exposed to different lighting conditions and found that a 21% increase in performance from students exposed to the most daylight when compared with those exposed to least daylight. Because many would doubt the results, the study was conducted in three different school districts with controlled demographics and teacher experience. In another long-term study, it was found that an average of 14% difference in test performance of students in daylit against non-day lit school facilities . 12 In 1999 a consulting group that specializes in building energy efficient structures rated the amount of daylight in 2000 classrooms for 21,000 elementary school students, in different schools on a scale of 0 to 5. They came to the conclusion that the students in classrooms with higher amount of daylight were 26% faster in reading and 20% faster in solving mathematics equations than the students in classrooms with less daylight. Another study concluded that people with depression symptoms who moved in more brightly lit buildings reduced their symptoms of depression by 11

19% .13 A 1992 study followed Swedish school children in four different classrooms for a year. The research showed that the kids in classrooms with the least daylight had disrupted levels of cortisol. Studies show that circadian rhythms keep the brain performing optimally by adjusting the levels of hormones and the metabolic state.14 Plenty of daylight in a classroom can boost alertness and help the body and mind to function better. Proper consideration when lighting a space can have a positive impact on peoples mood and behavior depending always on the usage of space. When considering the design of a building for learning activities for young children the quality of light should be a primary issue.

References: - 1: Tregenza P, Loe D. The design of lighting, New York : Routledge, 1998 . - 2-4: Tregenza P, Wilson M. Daylighting architecture and lighting design, New York : Routledge , 2011 . - 7-11: Dudek M. Schools and kindergartens, Berlin: Ria Stein , 2007 . - 5,6: Baker N, Steemers K. Daylight design of buildings, London: James and James (science publishers Ltd , 2002 . - 13,14: “Scientifuc American” http://www.scientificamerican.com/article.cfm?id=building-around-themind&sc=WR_20090428 . Accessed November 20, 2011 - 12: Nicklas M, Bailey G. Analysis of the Performance of Students in Daylit Schools. Proceedings of the National Passive Solar Conference , 1996 .

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3 . Health and the contribution of views through windows

Creating a window in a space has two visual functions, the daylight and the view. Daylight is the illumination that is coming through the window and view is what is seen when looking outside from the window. Accurately “ it is the daylight that carries the view,” 1 the perception of a view is one way that human body responds to daylight. When a person is in a room and looks outwards through a window the daylight has the ability to reach eyes from several angles. Some of the natural light arrives direct from the sky or even the sun. Even the exterior surfaces like the ground or the surrounding buildings outside the window or other elements like trees or flowers have the ability to reflect natural light. This is actually what makes them visible. The field of light has the ability to vary in intensity and color according its direction, “the miracle of vision is that we can use this complexity to construct an image of the world before us.” 2 When designing a school there are some rooms that must be windowless, with small openings or openings with the ability to the users to control the natural light or even to totally block it. For example amphitheaters when a screen presentation is in progress or laboratories with materials sensitive to sunlight. In general every room and space of the school facilities may need different treatment as it concerns the illumination.

There are two ways used to illuminate a room or a space with natural light. The side windows and the skylight.

Both ways provide to the user except from illumination, with

information about the outside environment, the weather or about the time of day. The side windows provides the users with another very important “element”, the view. In general any view is better than none but an attractive or interesting view is more preferable especially for a classroom or a learning environment. An attractive or interesting view can have a therapeutic effect for the users. Windows with views of nature and green spaces are proven to enhance work and well being, in antithesis views of buildings or urban environments can have the opposite effect.3

A negative side effect when having windows in your line of view is glare. The glare discomfort caused by a bright sky or by sunlight reflected from light colored surfaces is lower when there is a view of nature than a view of an urban scene of the same brightness. 4 There are several researches proving that classrooms with views towards nature and green areas can enhance learning abilities and concentration of the students.

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3.1 Building environments rich in nature views

The view that a person is able to have from a building can influence capability of the mind and more specifically the occupant's ability to concentrate and to reduce stress. Many people in the past decades claimed that the exposure to nature can be indeed beneficial . This belief has been tested empirically and in fact it is proven that exposure to nature is beneficial for human concentration, behavior and physical state. Although looking out of a window can be distracting, it turns out that views of natural settings, such as a garden, a field or forest, actually improve concentration.

In 2000 a study published by Nancy Wells, an environmental psychologist, resulted that viewing a natural environment can be helpful for people with attention and concentration problems. Wells evaluates the effects on concentration and attention on children’s from seven to twelve years old, and what effect the views from their windows have on them. They discovered that kids that have more views towards nature in their homes have increased attention span.5

Another experiment resulted that college students with views of nature from their dorm rooms have higher marks on measures of mental focus than students with views of entirely man made structures. In 2001 at the University of Illinois William Sullivan studied 96 children with attention deficit disorder, known as ADD. After the children started participating in activities like fishing, soccer and playing video games in which they were exposed in greenery and nature views , the parents reported that their children’s ADD symptoms were incredibly decreased. 6 In another study by Kenneth Tanner, head of the School Design & Planning Laboratory at the University of Georgia discovered that students in classrooms with unrestricted views of at least 15 meters outside their windows overlooking gardens, mountains or other natural elements, performed better in tests of vocabulary, language arts and math. In contrast, no increase in results for students in classrooms overlooking roads or parking lots. 7

Another study involving 656 randomly selected people has shown that the availability of a green outdoor environment at their workplaces showed a positive impact on stress. Comfort, pleasure and well being was witnessed between the participants. Even the view of a garden has shown positive results.8

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Numerous other studies as the above mentioned, have shown that when people look at nature views real or even projected on a screen can improve their ability to focus, concentrate and to reduce the effects that stress has on their mental and behavioral state.

References: - 1-3: Tregenza P, Wilson M. Daylighting architecture and lighting design, New York : Routledge , 2011 .

- 5 : http://www.graphics.com/modules.php?name=Sections&op=viewarticle&artid=852 . Accessed December 22, 2011. - 6 ,7: “Scientifuc American” http://www.scientificamerican.com/article.cfm?id=building-around-the mind&sc=WR_20090428 . Accessed November 20, 2011. - 8: “A Garden at your Workplace May Reduce Stress” http://www.bordbia.ie/aboutgardening/GardeningArticles/ScientificArticles/Garden_At_Your_Workplace_May_Reduce _Stress.pdf . Accessed November 20, 2011.

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4. The quantity of daylight and the users visual comfort

Designing a building and aiming to use natural light for the illumination of its spaces presents a question about how much light is proper and enough for the users and their needs. The quantity of natural light that is proper to be used for the illumination of a space depends on several parameters. It depends on the users, their age, on the activities and tasks that have to be performed, the usage of the building and even on peoples culture.1

“Examples of how much daylight is acceptable and normal for buildings can be found in several published guidelines and rules of thump.”2 The publications and regulations about daylight quantity refers on what each author considered to be the minimum acceptable requirements for satisfactory amount of daylight in a building, considering buildings of the time the author leaved rather than the conditions found in existing buildings of the time.3

Most of the writers give as required window sizes, in terms of the ratio of window area to the floor area or the ratio of window area to inside window wall area. Moreover some were more specific and recommended accurate proportions of windows and maximum room depth in relation to the height of the window. 4 What is worth mentioning is that recommendations about the window area for housing and schools stayed about the same. “The typical ranges of values for the floor area ratio in relation to the window area are for housing 8-13% and for schools a minimum 1725%.” 5 The regulations that give the minimum percentage on the analogy of the windows to the floor area or the wall area, are not enough to design a space “with natural light”. In a learning environment every day the users are carrying out a variety of visual tasks like reading and writing that place the correct and considered illumination of the space highly important. Visual tasks are not just writing and reading and are not just met only in learning environments. In every day life, in work, home, school or anywhere, people carry out visual tasks all the 16

time, mainly subconsciously. People are usually aware of the illumination of the space when there is too much or less light than they need to carry out with comfort their tasks. This occurs because “visual tasks are activities that require the brain to collect information from some specific part of the visual surroundings.”6 When the environment is not correctly illuminated then the users cannot carry out the visual tasks successfully or with comfort.

4.1 Light and the task

The most important visual tasks in a learning environment is reading and writing. But what is the relationship between the visual tasks and the illumination of the space? The amount of light in a space either natural or artificial that falls on a task (book, paper,board, screen, etc) is named as “task illuminance” 7 and can affect the users accuracy and speed of work.

Figure 1. Visual performance and task illuminance.

The amount of light falling on a task can have a noticeable effect but only up to a point. When for a example someone is reading from a book with the illuminance of a candle, adding a second and third one will make a significant difference. While reading the book in a bright environment adding additional illuminance will not make a significant difference and may not even be noticeable. We come to the conclusion that “there is a point beyond which additional light makes little improvement to the speed and accuracy of the task performance.” 8

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4.2 Minimum acceptable levels of illumination for schools

Classrooms, learning environments and studying areas within a school are based on deskbased activities. The users which are mainly the students and the teachers have to carry a variety of visual task in two and three dimensions, focusing on reading and writing on computers, on paper and black or whiteboard. To carry out visual tasks in a learning environment the user must adjust his vision from the board to the desk and from the desk to the board. It is important when designing a learning environment that the users may remain in the same position for long periods of time, an hour even more, and they may not have the choice to change position in the classroom. 9 The following table displays the minimum recommenced illuminance values for a variety of tasks in a school environment, according to data from the American National Standard Guide for School Lighting.

Table 1. Minimum recommenced illuminance values for school environments.

Moreover, there are four critical factors in desk-based work spaces, adequate task illuminance, a balance between daylight and electric light that maintains daylit appearance, a view to the outside environment and avoidance of direct or reflected glare. 10 18

4.3 When daylight is too much?

During midday the sun hitting the ground can be more than 100klx. For most people the tolerable amount of sunlight while reading a book outside is around 40klx. A large variation from when you compare the amount of light inside a building which is for a typical classroom around 500lx.11 In some field studies desktop illuminances of around 1500lx to 2000lx have been found to be too bright not because of the amount of illuminance but because of direct glare and glossy reflexions. Care must be taken to avoid large variation of brightness between surfaces at the far end of the room and those close to windows.12

4.4 Glare

Glare can be defined as a very harsh, bright, dazzling light and separated in two categories, the disability glare and the discomfort glare. “Disability glare is defined as the effect of stray light in the eye whereby visibility and visual performance are reduced.”13 Discomfort glare is defined as glare that produces discomfort and it does not necessarily influence visual performance or visibility.

A representative example of disability glare is the sensation that a person experiences on a sunny day surrounded by snow. The overall luminance levels of the environment is too great and bright for the eyes. An example of discomfort glare is what a person experiences when working on a computer screen and direct sunlight is falling in his field of view making it difficult to read what is on the screen because of the high luminance levels of the direct sunlight. 14 Studies on people reactions have shown that the discomfort from a small bright light depends on four factors: -the luminance of the light source -the size of the source -the luminance of the background -the angle of the source from the subject's line of vision . 15

The luminance and size of the light source have a direct connection with visual discomfort, as the light source luminance increases so does the discomfort. The luminance of the background and the angle of the source from the subject's line of vision reduce discomfort as they increase. This 19

points to the fact that the discomfort glare is the result of excessive contrast within our visual field.

The four above factors are important and particularly in cases were glare is coming from large sources, such as windows. When a large number of subjects are asked to describe the discomfort they have in various situations, the results show a wide variation. Other factors are the age of the viewer and the glare source. A large uniformly lit screen is found to cause less discomfort than a non uniform lit of the same brightness.

“It is not purely photometric characteristics that affect the sensation of discomfort: the viewer's interest in the glare source influences the degree of discomfort.”16

When the windows are facing views of natural scenes, like trees and water, are found to be less glaring than views of buildings, roads and urban landscape. The sensation of discomfort varies according to our interest in what we are looking at.

“A late-afternoon sky is beautiful and the beam from the setting sun that falls on the window gives pleasure, even though the glare index would predict it to be intolerably uncomfortable” 17

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4.5 Central and Peripheral vision

The fovea is a small area in the center of our eyes retina. When we look at something of interest we move our eyes so that the focus falls on the fovea, seeing the detail clearly. Everything that is focused on the retina outside the fovea is called peripheral vision. Even thought for much of the time people are not aware of it, peripheral vision is very sensitive to any movement and they depend on it to warn us of any change in the space around us. “Having the central field of vision only is like using a bright narrow-beam torch in a large dark unfamiliar room: you can see detail clearly but it is hard to gain a sense of the place as a whole” 18 A dim light may not be enough to allow us to complete our task but it allows us to see the size and shape of the room and get a sense of orientation. Peripheral vision is essential for our perceptual process as is our central field of vision. When light designing a space considerations must be made so no distractions fall in our peripheral vision, such as rapid movements or flickering lights. The illumination and color of our surrounding environment affect our visibility of the task at hand. 19

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4.6 Brightness adaptation

The physiology of the human body is able to adapt rapidly to the environmental changes that surround it. In hot weather the skin blood vessels dilate facilitating perspiration and in cold weather the blood vessels constrict in order to minimize heat loss. Also there are some long term physiological changes when a person leaves in hot or cold climates. One example of how the body adapts physiologically is the human eye. The eye has the ability to adapt to motion, color and to brightness. Over the period of day the lighting conditions change, the brightness may fall to a quarter of its original intensity, color may vary from blue to an orange white, the eye will act as a filter and block these slow changes leaving us unaware. The human eye has three mechanisms to adapt to brightness. First like a photographic camera aperture it adapts to brightness by opening and closing the iris. Second the eye's neuron's transform the sensory data in the eye-brain system providing immediate adaptation. The third mechanism in the photosensitive cells of the retina, is the bleaching and regeneration of pigment. The regeneration happens fast from dark to light but may take up to an hour for light to dark. 20

Figure 2. Brightness adaptation.

When there is a bright background and a dark center focus point the eyes cannot adapt because the large variation in brightness reduced the eye's sensitivity. In order to compensate for this phenomenon some design provisions must be made giving the users vision time to adapt. For example when entering and exiting a tunnel buffer zones of intermediate brightness must be used. When entering a cinema, zones of diminishing brightness are useful be used until the visitor enters the projection room. The spaces should comply to two requirements for people entering adapted to higher luminance. The light falling directly on the eyes is minimized so visual sensitivity is enhanced and essential objects and points of interest are sufficiently bright to be visible.21

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References: - 1-5, 8-12, 16-21: Tregenza P, Wilson M. Daylighting architecture and lighting design, New York : Routledge , 2011 .

- 6,7: Tregenza P, Loe D. The design of lighting, New York : Routledge, 1998 .

-13,14: “ResearcH JournaL, Understanding glare.”VOL 03.01 http://cms.perkinswill.biz/sites/default/files/PWRJ_Vol0301_04_Understanding%20Glare_0.pdf . Accessed January 3, 2012

Figures: - Figure 1, 2: Tregenza P, Wilson M. Daylighting architecture and lighting design, New York : Routledge , 2011 .

Tables: - Table 1: Dudek M. Schools and kindergartens, Berlin: Ria Stein , 2007 .

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5. Light on materials and surfaces

When illuminating a learning environment or a space with natural light the consideration of light in relation with the materials, surfaces and colors within the space is very important, in order to be able to choose which materials to use for certain circumstances. This chapter will explain the reflection and transmission of light on materials.

While illuminating a space light falls on the surface of the materials. Absorption, reflection and transmission are three possible processes that will happen when light falls onto the surface or layer of materials in the space.1

Figure 1. The three possible processes when light strikes on a surface or layer of material.

Reflection is when the light that strikes onto a surface is giving back an amount of the light received on it. a

Transmission is when the light that falls onto a surface is passing totally or partly through the material and derives to the other side of the material. b

In both of the above cases light or energy (light is translated into energy) can be absorbed by the material of the surface that it falls on. c a. light can be reflected: the ratio of the reflected energy to the incident energy is called reflectance R.

b. Light can be transmitted: the ratio of transmitted energy is called transmittance T. c. In both cases energy may be absorbed: the ratio of absorbed energy to the incident energy is called the absorptance,a. 2

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When considering reflectance, a surface with perfect black, that will reflect no light back at all will be 0 and a surface perfectly clear will be 1. All the real surfaces are above 0 and bellow 1. For a material that is opaque the transmittance is 0 and that is why the absorptance and reflectance possibility of materials are related as follows: R=(1-a)

3

The reflected energy equals the incident energy minus the absorbed energy. The incident energy is the light that strikes on the surface at a particular time.

Light on a transparent material is also reflected, transmitted and absorbed and so is related as follow: R=(1-a-T) (2) 4

In order to understand the difference between the materials it is worth mentioning that for an opaque material the absorption will take place on the surface of the material and for a transparent material the absorption will take place in the body of the material. This is the reason at the absorption depends on the thickness of the material. 5

The values of the materials can be a very useful tool when designing a learning environment. Certain materials can be used to improve the illumination and thermal performance of a space, to avoid glare or undesirable reflections. For example the thermal comfort of a space can be improved by the use of the correct materials. Specific glass can be used to reflect the sun's harmful radiation, to reduce heat transmission and control glare. Materials can be used to control and distribute light in a space.

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5.1 Diffusing and specular materials

In order to understand how specular and diffusing materials or layers affect a space,is important to understand how they interact with direct or indirect natural light. The properties of opaque or transparent vary as a function of the direction of incident light. It is easier to define this properties in relation to unidirectional or direct incident beam, such as the one by the sun or a distant point source. 6

Having an opaque surface that is described as specular this means that the material reflects the beam of light like a mirror. So when a direct beam of light is falling onto an opaque surface it gets reflected as a direct beam. The law of reflexion: angle of incidence i equals angle of reflection r, (i=r) 7

When a material that is transparent is described as specular then this means that this material has the ability to transmit a direct beam of light that fall on it without dispersing or diffusing it. Another ability of this material is the clear focused view when looking through it. 8 This kind of material is preferable to be used in spaces were clear connection with the outside is desirable.

The above two properties of materials opaque specular materials or layers and transparent specular materials or layers can have another ability, diffusion. When an opaque material has the ability of diffusion is referred as diffused reflector. A diffused reflector material is a mat surface that has the ability to reflect the light falling on the surface equally and in all directions (figure 3) in contrast with a material with specular reflection that reflects the light in only one direction (figure 2).

Figure 2. Specular reflectance.

Figure 3. Diffuse reflectance.

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When a material has the ability of diffused transmittance the light that falls on the surface of the material is transmitted thru the material as it happens on a material that is specular transmittable (figure 4). In the first case though (when the material has the ability of diffused transmittance) the light passing thru the material is distributed in the space equally and in all directions (figure 5).

Figure 4. Specular transmittance.

Figure 5. Diffuse transmittance.

The above four conditions (figure:2,3,4,5) represent cases that a direct beam of light is falling on a material or surface. When illuminating a space with natural light and for several reasons direct light in the space is not desirable , or when there is no direct light from the source, the sun, because the day is cloudy, then the natural light is a diffused light arriving from the sky and the sun but not directly in the space we want to illuminate. In those cases the natural light is considered that is arriving from a hemispherical source as it is shown in figure 6. 9

Figure 6. Light reflectance and transmittance patters for a hemispherical incident light source.

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References: - 1, 3, 4 ,6 ,9: Baker N, Steemers K. Daylight design of buildings, London: James and James (science publishers Ltd) , 2002 .

- 2, 5, 7, 8, 9: Tregenza P, Loe D. The design of lighting, New York : Routledge, 1998 .

Figures: - Figure 1 - 6 : Baker N, Steemers K. Daylight design of buildings, London: James and James (science publishers Ltd) , 2002 .

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6 . Daylight design in learning environments and the relation with the space

Designing a school building, each space must be considered separately for the light design but also together as a whole as a continuation one to another. The internal planning and the room layout of a learning environment is affected by the interrelationship between light design and spaces. For example when a user is walking through the hallway of the school going into a classroom or from a classroom going into the hallway, the light in the two spaces will play an important role. The transition from one space to the other will have an impact on the visual perception of the space entered. Entering from a bright illuminated space to a space of lower brightness will be perceived as entering a space with insufficient light even though the brightness of the space is satisfactory. As a consequence the user will have the need to illuminate the space with the use of artificial lighting.

In the opposite case, where the user is entering from a less bright room into a bright space with a significant difference in illumination levels the user will get the impression that the space brightness is too great. It is possible that the sudden brightness difference between the two spaces in his visual field will cause discomfort. As a consequence the user will have the need to lower the brightness by closing the shading devices available and create a space with insufficient brightness levels to perform with comfort the visual tasks required.1

This happens because human vision needs time to adapt to the significant variation of the light intensity between the spaces, as it was mentioned more analytically in chapter 4. A successful lighting design must consider human vision and make the transition from one space to the other as smooth as possible or by providing equal or not hugely different illumination variation. Correct light design can reduce the use of artificial lighting with positive impact on energy consumption.

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The case of Vanoise College

A representative example is that of the Vanoise College. The classrooms of the college are well illuminated with natural light and therefor to be avoided the discomforted between the transition from the classrooms to the circulation space, the circulation space has plenty of daylight too. At the ceiling of the circulation apace and the atrium space there is a skylight providing them with plenty of dynamic natural light, and moreover the daylight from the atrium is entered into the classrooms through high-level glazing, giving a balance between the two spaces and illuminating the classroom area with natural light free from glare. Also, the classrooms are illuminated with natural light from the opposite side with windows, something that is very important in order to achieve a balanced and an even distribution of daylight. 2

Figure 1. View of the circulation space.

Figure 2. Section showing the back of the classrooms being lit by secondary daylight from the atrium circulation space. The numbers are the light fluxes in lumens, for a total of 1000 lumens of incoming flux to each classroom.

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6.1 Natural light affecting and defining a space

Natural light in a space besides illumination, the connection with the outdoor environment and the benefits to the users health and performance abilities can affect and define a space. Light can: - give the opportunity to an architect to connect or differentiate spaces -be used to define different spaces within a large area -separate and define the activities within an area, according to the task and the users needs.3

The case of Rovaniemi library

An interesting example of how light can define different places in a large area is the Rovaniemi library in Finland by Alvar Aalto. In the library there are several different spaces within a large area. The areas are defined with the help of light design, natural and artificial, to separate rooms but at the same time is permitting visually and physically accessibility with each other. As a visitor is walking in the large space of the library he can see a display wall with exhibits that are illuminate with fluorescent fixtures hanging from the wall. Then the circulation corridor is defined by the two parallel lines of fixtures. One lane of round saturn rings and one of fluorescent disk fixtures. Then the visitors attention is drawn to the stairs leading to the lower floor and then to the circulation desk with a large rectangular skylight. At the same time a concentrated placement of disk fixtures points out the circulation desk. In the perimeter of the main hall there are bookshelves, illuminated with daylight from clerestory windows. Looking in the center of the main hall bookshelves “lining a reading area are highlighted from fixtures mounted at the top of the shelves, the yellow glow standing out against the crisp white light in the main hall beyond.” 4

Figure 3. Section of the Rovaniemi library. 1: Sunken reading area, 2: Main library hall, 3: Circulation desk, 4: Corridor

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Figure 4. Main hall with bookshelves at the

Figure 5,6 : Circulation area and main library hall.

perimeter. The area is illuminated with natural indirect light.

What the architect achieved by using light as a design tool and element is to differentiate those spaces without using any physical boundaries like walls and partitions. The spaces of the library are smoothly flowing one into the other and at the same time the user can realize the uniqueness of each space with the help of light. This kind of approach can be used in several buildings. At a library, at a working area separating offices in a company building or within a school. In order to apply that light design approach in a school building all parameters should be considered. The users and their needs, the academic program of the school and the facilities required for the school to function and which of them can coexist in the same area without any physical boundaries. Separating from each other facilities and activities that take place in a school with light design can provide the space and the users with several advantages. The users, students, teachers and visitors will be able to coexist and carry on several activities in the same space giving them the chance to interact with each other, cooperate and socially mingle.

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6.2 Natural light connecting interior spaces

Light design can give the possibility to connect rooms and spaces within a building even when there is the need to be “separated from each other physically, thermally and acoustically.” 5 This is possible to be achieved with the use of natural light and the use of materials and partitions that have the ability to let the light through them partly or totally. Glass partitions or PVC partitions can connect rooms and spaces with each other providing also either clear visual connection between the spaces or semi visual connection and also illuminate the space by borrowing light from the other spaces. Depending on the usage of the room and the users need the materials and the transparency of the partitions can be changed.

The light can be be borrowed through transparent or semi transparent partitions of the rooms. When for example there is a space with direct access to daylight light can be delivered to an interior room next to it that has no or limited daylight access. Using this method an interior space with no windows can have a visual access to the space with direct natural light and possibly to the outdoor environment and therefor to the views. Moreover this method gives the sense to the users of both spaces that the available space is expanded even when the partitions are semi transparent.

Another very important advantage when illuminating by borrowing light from another space that is illuminated with natural light is to eliminate the use of electric lighting and save energy. Placing the glass or PVC partitions above the users eye level or using materials such as frosted glass, semi transparent materials provide visual privacy for a space when required.

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The case of the Apollo Montessori school in Amsterdam

An example of light connecting interior spaces is the Apollo Montessory school in Amsterdam, designed by Herman Hertzberger. Between the classrooms that face the exterior space of the school and the interior central hall, glazed partitions are placed. Both spaces have the ability to exchange light and views. The large glass partitions at the top of the walls between the classrooms and the central hall transmit light and views both ways. What the architect achieved is to illuminate with natural light the edges of the central hall and the classrooms from all sides giving a balanced and uniform illumination in the classrooms that is required to carry successfully the visual tasks and the learning teaching procedure form the students and teachers. From the central hall the users can see into the classrooms and vice versa. At door height there is a lower glazing giving direct visual interaction at the entries of the classrooms. 6

Figure 7. Section of the Apollo Montessori school. 1: Classrooms, 2: Central circulation hall.

Figure 8. Communal hall.

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References:

- 1,2: Baker N, Steemers K. Daylight design of buildings, London: James and James (science publishers Ltd) , 2002 .

- 3- 6: Millet M. Light revealing architecture, 1996 .

Figures: - Figure 1: http://www.ac-grenoble.fr/college/lavanoise/cariboost_files/IMGP1760.JPG

- Figure 2: Baker N, Steemers K. Daylight design of buildings, London: James and James (science publishers Ltd) , 2002 . - Figure 3: Millet M. Light revealing architecture, 1996 .

- Figure 4-6: http://media.finnair.com/Rethink/quality/wp-content/uploads/2010/10/IMG_3751.jpg

- Figure 7,8: http://hertzbergertca.blogspot.com/2009/10/apollo-schools-montessori-school-and.html

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7. Approaches and daylighting systems for optimum quality and quantity of Natural light in learning environments

When designing a learning environment the approach made from the architect in order to achieve the optimum quality and quantity of natural light in a learning space is different from other buildings. The orientation of the building is very important to maximize the use of natural light in a learning environment. Elongating the building along an east-west axis is a good approach. Placing windows at the north side of the building where the diffuse daylight is available and at the south side where summer and winter sunlight is relatively easy to be controlled. Windows that are placed high in the wall, for example clearstoreys or tall side windows can maximize daylight distribution and bring light deeper into the space. Further more the light should be delivered into the space (especially the classroom) from two sides in order to reduce luminance contrast and shadows on the working area, but never opposite or behind the board because in such case it will be difficult for the students to see because of glare and light contrast. Indirect daylight into a classroom is a good way to control sunlight and the negative effects such as heat gain, glare and discomfort. The materials of the windows are another very important factor, in some cases the glass that is going to be used may need to be translucent, in order to avoid direct sunlight or to diffuse the light into the space. The materials, textures and colors in the space should be chosen carefully and according to how the light will react on them. For example the use of high reflectance interior surfaces, especially on the ceilings so the light will be reflected into the space and avoid reflectance surfaces or bold colors on the walls and on desks. The following figure1 illustrates the permitted reflectance values for a classroom.1

Figure 1: Recommended surface reflectance values for classrooms.

Finally, it is of great importance that the architect will provide the users control of the amount of light entering the space when necessary, according to the various activities that will take place. This control can be achieved with manual or electrical louvers, curtains or blinds. It is

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equally important to consider the material and the color of those devices.

Below are the basic daylight principles for a learning environment:

-Avoid direct sunlight penetration into glare-sensitive teaching areas and spaces -Use gentle, uniform light throughout the space -Prevent glare -Provide control mechanisms such as louvers, curtains and blinds -Electric light should complement daylight design and maximize energy savings through the use of lighting controls -Integrate designs of exterior and interior spaces to maximize use of natural light such as avoidance of placing skylight where it might be shaded by a tree. 2

Windows, skylight, top lighting, and glazed doors are efficient design elements that can be utilized in employing natural light in the learning environment. These elements should be carefully integrated in the design process through placement, location, selection of materials, and shading.

7.1 Daylighting systems

What daylighting systems do is to harvest the available daylight and distribute it inside the room. The systems belong in two general categories, the top-lighting systems and the side-lighting systems. Top-lighting systems distribute the available daylight inside the room from the ceiling or the roof of the room and side-lighting systems distribute the available daylight from the sides of the room. The following examples present examples of the two mentioned categories and how the available light reacts on each case.

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Side windows

The levels of light in a room with side windows are higher near the window and lower away from the window. The height of the window in a space can effect the depth of illumination with daylight.

For example in a case of a classroom with a low ceiling and grade depth “could

experience a gloomy feeling due to the disparity in light levels between the back of the room and the peripheral area near the window.”3 In such case an effective strategy for the illumination of a classroom can be achieved by making the depth as much as 2 ½ times the height of the window

above the working area. “For example, a classroom with a ceiling height of 3.5 meters, which is the usual for a classroom, and desk height 0.75 meter, if the top of the window is 2 meters above desk height, the area that is adequately daylit is approximately up to (2 x 2.5 meters) 5 meters deep from the wall.”4

Figure 2: A narrow window allows narrow daylight distribution in the space,the effected area depends on the height of the window. Figure 3: A large window allows a wider daylight distribution in the space,again the effected area depends on the height of the window.

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Light shelves

Designing a classroom with side windows, an architect should give attention in order not to create areas near the windows that are going to be ''very brightly lit'' and areas at the back of the room that are going to be dark. Light shelves could proved a good solution at this problem. They are designed in such way that the clerestory portion above the light shelf catches sunlight or diffuses daylight and reflects it toward the back of the room away from the window. The protruding portion of the light shelf, in the case of a combined or exterior light shelf, acts also as a shading device and prevents sunlight from falling directly on the work. Moreover it prevents glare and minimizes the brightness near the window. As a result the light levels in the room are more uniform. The clerestory portion of the window is preferable to be made of clear glass for maximum daylight harvesting. The lower portion below the shelf if exist, is referred to as the view window. The glass in it is preferable to be tinted to reduce glare.5 In the case that the view is provided from other windows, for example northfacing windows the lower portion could be of a semitransparent class or material in order to distribute diffuse light in the space and avoid glare.

Figure 4: Daylight distribution in the space with light shelf and without light shelf.

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Skylights

Skylights are used for single-storey schools and is a top-lighting strategy. They distribute natural light from the top of the building. Figure 7 presents the recommended spacing between skylights as function of the mounting height of the skylight, or the distance between the bottom of the skylight and the work-plane. The depth and the size of the opening of the skylight effects the efficiency of the system. If the skylight well is too deep or too dark a large amount of the luminous energy incident on the outside of the skylight is possible to be lost. The size of the opening also effects the daylight distribution in the space. More over is better to be used more than one skylights within a large area in order to balance the daylight levels inside the space. 6

Figure 5: Top-lighting strategy with a single skylight.

Figure 6: Top-lighting strategy using two skylights,the light distribution in the space is balanced in contradiction with the strategy with the one skylight.

Figure 7: Recommended distance between skylight features for uniform daylight distribution in the space.

Figure 8: A single skylight feature in a large area it is possible to create large differences between the light levels in the space.

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Clearstory windows

Clerestory windows have the ability to distribute natural light deep in to the room and if exist another side window they provide a more balanced light distribution in to the space. The relationship between illumination from side window and clearstory depends on their size, height and position. “With a typical narrow window arrangements for clearstories, the recommended depth from the plane of the clearstory to the opposite wall is about equal to the distance from the mounting height of the clearstory above the workplane level.

For wider

clearstories the depth could be one and a half the mounting height. To obtain adequate and more uniform daylight distribution, the height of the clearstorey window should be about one half the side wall window height. Moreover not only the height of the clearstorey windows affects the depth of the daylight distribution in the space but also the width of the clearstory window.” 7

Figure 9: Clearstories allow the daylight to reach wall opposite the clearstory wall. Figure 10: Large clearstories allow deep penetration and large amounts of daylight. Adding a clearstory to a side window provides a balanced daylight distribution in the space.

Figure 11:Combining a side window and a clearstory results in deep and uniform daylight destribution in the space

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Sawtooth systems

Sawtooth systems are a good daylight system for a large classroom when uniform light distribution is desired. Especially, if the openings of the system are facing south, and the day is sunny then directionality of light distribution can be achieved in the space under these systems. On an overcast day, though, sawtooth systems can provide a little more uniformity than on clear days. “In general daylight levels are higher towards the end of the room that faces the opening. The spacing between sawteeth is recommended to be 2 ½ H, with (H) being the height of the ceiling clearance.”8

Figure 12: Daylight distribution from a sawtooth system. Case 1: clear sky,aperture facing sun. Case 2: overcast sky. Case 3: clear sky, aperture opposite sun.

Figure 13: Recommended distance between the openings.

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Roof monitors

Another good daylight strategy for a large classroom when uniform light distribution is desired, is

the roof monitor.“ Roof monitors bring in light from above from two opposite

directions. Henceforth directionality of light is minimized and uniformity is maximized. Roof monitors can be designed to allow sunlight in winter if desired and block it in the summer when not desired.”9

Figure 14: Roof monitors allowing winter sunlight and blocking summer sun.

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Anidolic systems

Anidolic systems are designed in such way to be able to collect the incident sunlight that falls on an entry aperture and concentrate it on a smaller exit aperture where the receiver is placed. “The receiver is a light emitting source or a highly efficient luminaire capable of controlling beam output through well-defined beam spread. The protruding portion of the system acts as a solar collector and concentrator. It collects large amounts of sunlight through the entry aperture and concentrates it onto a smaller area where the diffuser or distributor is located near the exit aperture. The distributor spreads daylight over a larger area further away from the side wall window.”10

Figure 15: Anidolic system collecting sunlight and distributing it towards the back of the classroom with concentrating mirrors and distributors.

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7.2 Case studies

The following case studies of schools present the daylighting strategies that are followed in order to achieve well day lit design but also energy-efficient design.

1 . The Dalles Middle School at Oregon

The Dalles School District incorporated lots of natural light to reduce the need for electric lighting and the associated increase in the air conditioning load. More importantly, studies show that students perform better when skylights and windows bring natural, non-glare light inside the classroom.

The Dalles Middle School has incorporated daylight into each classroom and other facilities using the following methods:

- The school is oriented so classrooms face north and south.

- The large windows have a special glazing to minimize glare and heat, but bring lots of natural light inside the room.

- Light “shelves” are built on the outside and the inside of the windows. These three-foot reflective projections are located about a third of the way down the window. They reflect the sunlight to the white ceiling which “bounces” the light deeper into the room. The shelves also shade the lower window and reduce heat gains into the room caused by the sun.

- One or two light tubes are located on the inside wall of the room to bring in additional natural light. The light tubes are much smaller diameter than a skylight and made of reflective material to bring direct sunlight and ambient light through the ceiling and into the room. A diffuser spreads the light evenly. Near the light tubes, three high windows within the classroom allow some of the light into the interior hallway. Both the first and second floors have light tubes and light shelves.

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-Windows that face west have vertical sunscreens that provide shade in late afternoon without blocking the view.

- In the gym, several interior skylights are lined with a spun fiberglass. This diffuses the light so there is no direct sunlight on the gym floor. 11

Figure 16: Light tube provides light in interior wall area. High windows on the interior walls allow light into the hallway.

Figure 17: Natural light comes into the interior hallways of the school from high windows on the interior walls of classrooms.

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Figure 18: Gym skylights are lined with spun fiberglass to diffuse natural light. Figure 19:the vertical louvers reflect the direct sun and allow the the natural light during summer.

Figure 20: Exterior view of the school with light shelves.

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2. Durant Road Middle School, North Carolina

The Durant road middle school at North Carolina is another case that applied daylighting design strategies at the design of the school building. The daylighting strategies used are serving the purpose of maximizing the quality and quantity of natural light in the school facilities but also sustainable purposes. “The energy saving features used at have reduced the energy use for lighting, ventilation, and heating by 50%.60%.”12

More over the daylighted classrooms have increased the well being of the students and the teachers and it is partly responsible for the record high attendance rates. “We are running about 3% ahead of the rest of the county in attendance, '' as Tom Benton, principal of Durant Middle School said .”13 The Durant road middle school has incorporated daylighting into each classroom and other facilities using the following methods:

- Orientation of the building is lengthwise on an east/west axis to optimize placement of the north and south facing daylighting monitors and to reduce heat gain.

-

South-facing and north-facing roof monitors provide daylighting to classrooms, cafeteria,

gymnasiums, and hallways with a corresponding 30% overall increase in glazing for daylighting and an absence of glazing on the east and west sides.

- The roof is equipped with a radiant barrier that reflects more than 90% of the radiant heat. There is low-e glazing throughout, including the roof monitors.

- High-efficiency lighting equipment and controls are used, including motion sensors and lightlevel sensors to automatically adjust energy-efficient fluorescent lighting as needed.

- An energy management system controls the amount of outside air circulation to correspond with the occupancy level of the school, rather than constant operation, which is typical of school buildings.

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- The school’s natural daylighting is supplemented by electric lights controlled by automatic dimming controls that activate or dim lights as daylight levels fluctuate. In 1997, the American Institute of Architects voted the design of Durant Middle School as one of the top ten most environmentally friendly buildings in the United States. 14

Figure 21: Interior view of a classroom with a skylight.

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3. Homewood Middle School at Alabama

At the Homewood middle school daylighting is one of the primary strategies to achieve adequate lighting in the building but also to achieve energy-efficiency of the building by using the following features:

- The ninety-five percent of the school is day-lit, and all classrooms in the school have exterior windows ,this is used also to enhance views towards nature as it can be seen from the images.

- Shading devices, such as overhangs, are used on the south side of the school to reduce solar heat gain and glare in the school.

- Light shelves at the south are used to distribute light deeper into the school building and the classrooms.

- The windows on the north side of the school are large to increase the amount of daylight in the school and the classrooms.

-The electrical lighting is controlled by photo sensors and occupancy sensors to make use of available daylighting and reduce electricity usage.15

Figure 22: Exterior view of the Homewood middle school.

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Figure 23: Building exterior with light shelves.

Figure 24: Media center with Large north-side windows

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Figure 25: Typical classroom with nature view.

Figure 26: Gym entrance

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References: - 1,2: United States Department of Energy. National Best Practices Manual for Building High Performance Schools , 2010 . - 3-10: Dudek M. Schools and kindergartens, Berlin: Ria Stein , 2007 . - 11: http://www.oregon.gov/ENERGY/CONS/school/docs/thedalles.pdf - 12: http://wattwatchers.utep.edu/daylight.html, - 13: www.inovativedesign.net/schools - 14: http://www.eere.energy.gov/ -15: http://www.ceee.uni.edu/Portals/0/Documents/Energy/SchoolEnergyEff/AEDG3_K12.pdf

Figures: - 1-15: Dudek M. Schools and kindergartens, Berlin: Ria Stein , 2007 . - 16-20: http://www.oregon.gov/ENERGY/CONS/school/docs/thedalles.pdf - 21: http://hpb.buildinggreen.com/cgi-bin/projectscale.cgi?max=350&src=/project_46/Daylighting.jpg - 22-26: http://apps1.eere.energy.gov/buildings/publications/pdfs/energysmartschools/ess_homewood-middle_cs.pdf

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Conclusion Implementing natural light in a learning environment is of a great importance. Learning performance and health of students can be affected positively if the daylight design of a learning environment is correct and negatively impacted with it's absence. Furthermore the correct implementation of natural light prove beneficial for the building's energy efficiency.

Providing natural light in a learning environment through side windows and skylights can have another positive impact, can give information about the weather and the outdoor environment. Side windows can also provide the users with views of natural scenes such as trees and gardens that are more preferable than views of urban scenes, since it is proven to enhance users health and learning performance. Moreover are found to be less glaring in comparison with views of buildings, roads and urban landscapes.

The consideration about the quantity of natural light and the users visual comfort is a very important aspect when designing a learning environment with natural light and it depends on several parameters such as the usage of every space within a school and also on the activities and the tasks that have to be performed in every space.

Despite considering each space separately, for the light design, the school building must be considered as a whole in order to create spaces that the user will not experience any discomfort when moving from one space to another because of the difference between the illumination levels.

Natural light can illuminate a space, connect it with the outdoor environment and improve the users health and academic performance. Even more, the use of natural light in a space can affect and define a space, giving the opportunity to the architect to connect or differentiate spaces within a large area with out using physical boundaries. Successful implementation of natural light in a learning environment can be achieved with the correct use of daylight systems and principles.

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Bibliography:

- Baker N, Steemers K. Daylight design of buildings, London: James and James (science publishers Ltd) , 2002 . -Clay F. Modern school buildings. London: Batsford , 1929. -Dudek M. Architecture of schools-The new learning environments , 2000 .

-Dudek M. Children's spaces , 2005 .

-Dudek M. Schools and kindergartens, Berlin: Ria Stein , 2007 .

- Millet M. Light revealing architecture, 1996 .

-Nicklas M, Bailey G. Analysis of the Performance of Students in Daylit Schools. Proceedings of the National Passive Solar Conference , 1996 .

-Tregenza P, Loe D. The design of lighting, New York : Routledge, 1998 .

-Tregenza P, Wilson M. Daylighting architecture and lighting design, New York : Routledge , 2011 .

-United States Department of Energy. National Best Practices Manual for Building High Performance Schools , 2010 . -Heschong Mahone Group. Daylighting in Schools - An Investigation into the Relationship between Daylighting and Human Performance,” prepared for Pacific Gas & Electric Company and funded by California utility customers, 1999. -Kuller R, Lindsten C. Health and behaviour of children in classroom with and without windows. Journal Environmental Psychology , 1992 .

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-Building-around-the-mind ,Scientific American. http://barlab.mgh.harvard.edu/papers/ScientificAmerican09.pdf Accessed November 20, 2011 -“Stress and Concentration” http://www.holisticonline.com/stress/A2005/stress_stress-andconcentration.htm. Accessed November 20, 2011 -“Scientifuc American” http://www.scientificamerican.com/article.cfm?id=building-around-themind&sc=WR_20090428 . Accessed November 20, 2011 -“How rooms and architecture affect mood and creativity.” http://blog.ounodesign.com/2009/05/02/how-rooms-and-architecture-affect-mood-and-creativity. Accessed November 20, 2011 - “ResearcH JournaL, Understanding glare.”VOL 03.01 http://cms.perkinswill.biz/sites/default/files/PWRJ_Vol0301_04_Understanding%20Glare_0.pdf . Accessed January 3, 2012

- “A Garden at your Workplace May Reduce Stress” http://www.bordbia.ie/aboutgardening/GardeningArticles/ScientificArticles/Garden_At_Your_Work place_May_Reduce_Stress.pdf Accessed January 3, 2012 - http://www.graphics.com/modules.php?name=Sections&op=viewarticle&artid=852 Accessed January 3, 2012 -http://www.ceee.uni.edu/Portals/0/Documents/Energy/SchoolEnergyEff/AEDG3_K12.pdf Accessed January 3, 2012

-http://wattwatchers.utep.edu/daylight.html, Accessed January 6, 2012

-http://www.eere.energy.gov/ Accessed January 3, 2012

-www.inovativedesign.net/schools Accessed January 3, 2012

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-http://www.oregon.gov/ENERGY/CONS/school/docs/thedalles.pdf Accessed January 3, 2012 -http://www.nrel.gov/docs/fy00osti/28049.pdf Accessed January 3, 2012

-http://hpb.buildinggreen.com/cgi-bin/projectscale.cgi?max=350&src=/project_46/Daylighting.jpg Accessed January 10, 2012

- http://apps1.eere.energy.gov/buildings/publications/pdfs/energysmartschools/ess_homewoodmiddle_cs.pdf Accessed January 12, 2012

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