Abstract

The study focuses on analysis of visual performance and quality issues in classrooms located in the United Arab Emirates (UAE). The methodology depended on data collection and analysis of design information obtained from architectural drawings of standard schools, design compliance documents set by the relevant governmental bodies, and site visits and photography. It analyzed several important design issues that have significant impact on visual quality, including space size and depth to height ratio, windows orientation, lighting direction and desk position. It used simulation to investigate potential visual problems during critical times and view angles. Several problems concerning contrasting luminance levels in the field of view were identified and described. Mitigation of the problems using recommended daylighting systems was discussed based on the UAE climate.

INTRODUCTION

The United Arab Emirates (UAE) lies between latitudes 22°–26.5°N and longitudes 51°–56.5°E. Being on the tropic of cancer (24°N) results in that the UAE region receiving the highest annual rate of solar radiation. In such a harsh climate of the UAE, which is characterized by high levels of solar radiation and intense sunlight, the proper window design is the one which minimizes direct sunlight by means of shading and provides diffuse daylight reflected from the ceiling.

Most buildings in the UAE are not designed to achieve proper shading or improve visual quality. In school buildings, many classrooms and other educational spaces such as laboratories, art rooms and libraries experience direct sunlight due to inappropriate solar orientation (e.g. west or east). One can also find many educational spaces designed with deep spaces that are lit from one side, and in other cases, educational spaces with windows either facing the students' eyes or to the rear of students' desks (Figure 1). This creates serious problems of high brightness contrast and acute glare that result in deteriorating visual comfort and in some cases causing health problems; ‘the most common complaints caused by visual work in poor conditions are eyestrain in various forms, muscular aches and pain, and more general reactions such as fatigue, irritability and headaches’ [1]. In addition, many school buildings incorporate large areas of glazing that are designed without shading. This results in admitting high amounts of solar radiation into the indoor spaces. To compensate for the increased cooling and lighting loads, the size and operation of building systems has to be oversized, and therefore, much more energy is consumed.

Figure 1.

Typical visual problems due to poor lighting design in classroom spaces in the UAE: high brightness of light source—the window (a), acute contrast between light source and surrounding surfaces (b), veiling glare on students' desks caused by scatters of sunlight (c), and acute contrast and veiling glare on whiteboard (d).

Figure 1.

Typical visual problems due to poor lighting design in classroom spaces in the UAE: high brightness of light source—the window (a), acute contrast between light source and surrounding surfaces (b), veiling glare on students' desks caused by scatters of sunlight (c), and acute contrast and veiling glare on whiteboard (d).

The Educational Buildings Planning Department of the Ministry of Education produced a list of compliance conditions for school building design [2]; some of which are related to provision of lighting in classrooms: it states that lighting should come from the left side of students and not from the opposite side of the blackboard; it also states that classrooms should have openings for natural lighting and ventilation with total area not <20% of the floor area. A preliminary study, done by architectural/engineering consultants [3] for the Ministry of Public Works and Housing to evaluate schools and kindergartens in the UAE, recommended relying on natural lighting whenever possible, use shading devices on windows and using low energy artificial lighting with high-efficiency fluorescent lamps. The purpose of this study is to identify problems associated with classroom spaces design in the UAE with regard to visual performance and quality.

BACKGROUND

In teaching zones of schools, lighting requirements are most strict. Problems arise when lateral illumination results in non-uniform distribution of light. These problems are apparent when exposure to natural lighting is limited; that is, when the classroom's outside wall has a relatively short width compared with the space's large depth. This design configuration of classrooms is usually used to limit the size of circulation corridors and reduce building costs. To improve daylighting behavior in these types of buildings, there are several recommendations [1]. Courtyards, atria and galleries are highly recommended. The first two are used for illuminating adjacent interior spaces. Galleries can be used for illuminating hallways and common areas. Light-wells and sun-pipes can also be useful to reinforce the illumination of interior zones of classrooms and corridors. The most commonly used lateral pass-through component is windows. Clerestories and skylights can also be used to supplement the illumination provided by windows in classroom zones.

A previous study [4] analyzed daylighting potentials for different orientation in a public school in Curitiba, Brazil, using simulation. The aim was to create guidelines that can facilitate site planning of the school building. The percentage of adequate illumination on school tables and the balanced distribution on opposite sides for each condition was used as an indicator of the overall daylighting performance of the classroom. The highest daylight distribution index was found in the N–S axis orientation (windows exposure to E and W) when there is no shading (0.70), and in the NE–SW axis orientation (0.77) and the NW–SE axis orientation (0.81), when shading elements are used for clear and overcast skies, respectively.

Quality daylighting can be achieved by blocking direct sunlight while encouraging reflected sunlight. At all times, the light should be diffused by reflecting it off the ceiling; in all cases, it must be shaded before it enters the space [5]. Solar filters are needed to screen and filter direct solar radiation, as well as to avoid glare and contrast problems. These can be fixed or movable such as louvers or brise-soleil. Light shelves, overhangs and baffles can be used to improve the lighting distribution in classrooms and avoid glare. The light shelf may redirect direct sunlight and shade the room as well as being used as a redirection system for diffuse light [6]. Light shelves have the potential of improving daylight distribution by increasing light levels at the back of a room while reducing the high levels of daylight near the façade [7]. Plants can also provide sun shading and improve the quality of daylight entering through windows by scattering direct sunlight and reducing its intensity while moderating glare coming from the bright sky [4]. Another study [8] in the UAE recommended using solutions that can help to redistribute and filter the daylight such as plants and trees in desert climates even for North façades.

Light shelves and other systems (Prismatic glazing, prismatic film and mirrored louvers) were tested at the Building Research Establishment [9], and the results indicated that these systems reduced illuminance levels throughout the space compared with unshaded windows. All tested systems improved uniformity and had the potential to reduce glare from the windows. By redirecting rather than eliminating this light, innovative daylighting systems could provide shading without massive reductions in internal illuminances. Another study [10] showed the potential of light shelves to improve daylight distribution in classrooms in Parana, Brazil. It compared the lighting levels and distribution for a classroom with light shelves and having a window to floor area ratio of 0.13 versus another one without light shelves and having a window to floor area ratio of 0.45. The results showed that the independent use of the light shelf permitted a more uniform indoor lighting, yet with reduced indoor lighting levels (around 50%). Although this could result in increasing the use of artificial lighting in the light shelf case to compensate for the reduction in lighting levels, the expected visual and thermal comfort due to solar shading and more uniform light distribution would make the light shelf case a better option. The light shelf, when combined with overhang from outside, can help to block direct sunlight and reduce solar gain. This issue is very significant in hot climates like the UAE because of the intense direct sun load that can cause high levels of thermal and visual discomfort in addition to high levels of cooling energy.

METHODOLOGY

In order to identify the problems associated with classroom design with regard to lighting conditions and visual performance, the study used the following methodology.

Design information survey

The study conducted a survey of architectural design information of typical schools in the UAE that included field visits and collection of data from several documents: architectural drawings of seven prototypes used by the government to build public schools, compliance conditions for school building design that is enforced by the Educational Buildings Planning Department of the Ministry of Education [2] and consultant studies developed for the Ministry of Public Works and Housing to evaluate schools and kindergartens in the UAE [3]. These documents were obtained from several sources such as the Ministry of Education and the Ministry of Public Works.

Design information analysis

The school design, with specific focus on classrooms, is analyzed with regard to several parameters: classroom size and depth–height ratio, window orientation, lighting direction and desk position. These are the factors that have significant impact on natural lighting performance and quality inside classrooms. The analysis is based on agreement of these factors with the compliance conditions for school building design set by the UAE Government [2], recommendations of government consultants [3] and previous research findings and design rules of thumb.

Classroom size and depth to height ratio

The depth to which natural lighting can reach with useful sufficient illuminance levels (i.e. 300 Lux) [1], depends on the classroom size and its depth–height ratio. Adequate daylight can easily be introduced up to 4.6 m with a conventional height window (around 3 m). New technologies can passively redirect light to greater depths (4.6–9.1 m). A room with a height to depth ratio of 1:2 with 20% glazing of its external wall area allows good penetration of daylight (1.5–2 DF) and can be described as cheerfully day lit [11]. The government compliance conditions for school building design [2] require (in item 17) that classrooms should have openings for natural lighting and ventilation with total area not <20% of the floor area.

Window orientation

Natural daylighting through North windows does not cast shadows on the task; accordingly, it is recommended for illuminating classrooms and other teaching spaces because it is composed mainly of indirect diffuse light coming from the sky. Direct sun on North orientation can be experienced in only very short periods in the early morning or late afternoon during the middle of the summer when schools are closed.

Lighting direction

Another important issue that has impact on the visual performance of the student is the lighting direction inside the classroom with regard to the desk position. The government compliance conditions for school building design [2] require (in item 4) that lighting should come from the left side of students and not from the opposite side of the blackboard.

Critical desk positions

The location of the student desk inside the classroom has a great impact on the visual comfort of the student. Each student position has a different field of view, which is a function of the viewer point and the center of interest (on the task). Contrasting luminances in the field of view should be comfortable and aid to improve visual performance. It is desirable to make the visual task the brightest object in the field of view. According to previous findings in the literature [1], the following luminance ratios within the field of view should be aimed at: between task and darker surrounding 3:1; between task and remote darker surfaces 10:1; between light sources and surroundings 20:1; maximum contrast 40:1; and highlight object for emphasis 50:1. Also, luminance levels as a function of position in the field of vision should be within acceptable levels, as defined in the literature [1]. They are shown in Table 1. These values are used in this study as benchmarks to investigate visual comfort problems caused by classroom design.

Table 1.

Field of view and acceptable luminance levels [1].

Position Luminance levels (cd/m2
45° 2500 
35° 1800 
25° 2500 
15° 1250 
graphic 
Position Luminance levels (cd/m2
45° 2500 
35° 1800 
25° 2500 
15° 1250 
graphic 

The visual axis is a straight line connecting a viewer point (of a student seated on his/her desk) with a center of interest (located on the whiteboard). There are a huge number of combinations between viewer points and centers of interest inside a classroom. It would be unrealistic and probably unnecessary to investigate all possible combinations. A simpler and logical way is to test the extreme locations and choose the most critical ones based on testing. To compare visual performance among different fields of views, a critical center of interest should be identified. To do this, two extreme points of interest were compared using simulation: one on the far left side and another one on the far right side, of the whiteboard. The results of these initial runs showed more visual problems in the field of view of the left point. That is because of its proximity to the light source (i.e. the windows), which caused a sharp contrast of luminance levels between the task (i.e. the whiteboard) and the darker surrounding (i.e. the front and side walls), and also between the light sources (i.e. the windows) and the surroundings (i.e. the front and side walls). After identifying the critical center of interest, it was required to identify the critical viewer point based on testing. The viewer points located near the corners of the classroom are the extreme ones; these are denoted by the letters: A, B, C and D in Figure 2. Each of these points has a visual axis pointing toward a center of interest on the whiteboard. On the basis of schematic analysis of classroom design geometry and field of view, viewer points D was judged to be less critical than the other viewer points. Because of its location (in the front of the classroom), the field of view of point D barely sees the sources of lights (i.e. the windows), and accordingly, it was ignored. For the other viewer points, simulation was used to identify the most critical one. The results are explained later in Section 4.

Figure 2.

Camera simulation and field of view from three critical desk positions: A, B and C.

Figure 2.

Camera simulation and field of view from three critical desk positions: A, B and C.

Simulation planning and conditions

After collection of data and analysis of classroom design, planning the simulation runs and determining the simulation conditions was required. This included the following.

Classroom design and building materials

The design information obtained from the survey was used to create a 3D model for a space representing the standard classrooms in the UAE; this model was used in the simulation runs. A summary of the design information and building materials properties of the classroom model used in the simulation is described in Table 2.

Table 2.

Design information and building materials properties of the classroom model used in simulation.

Item Properties Remarks 
Walls, ceiling, window sill Material: Off-white paint Classroom size is 6 × 8 m (48 m2
 Reflectance: 68% Classroom height: 3 m 
Glazing Material: Clear coated low-E Properties reflect common construction materials used in the UAE school buildings 
 Transmittance: 75.30%  
 Reflectance: 11.20%  
 Thickness: 3.84 mm  
Window frame Material: Brushed aluminum  
 Reflectance: 79%  
 Specula: 50%  
 Roughness: 10%  
Item Properties Remarks 
Walls, ceiling, window sill Material: Off-white paint Classroom size is 6 × 8 m (48 m2
 Reflectance: 68% Classroom height: 3 m 
Glazing Material: Clear coated low-E Properties reflect common construction materials used in the UAE school buildings 
 Transmittance: 75.30%  
 Reflectance: 11.20%  
 Thickness: 3.84 mm  
Window frame Material: Brushed aluminum  
 Reflectance: 79%  
 Specula: 50%  
 Roughness: 10%  

Sky conditions

Clear sky with sun conditions are used based on Dubai location coordinates (latitude 25°16' N, longitude 55°20' E). Simulating the entire year would be very costly, and yet it is probably not necessary if one can decide on important dates and hours. The standard school year (September to May) and school hours (8:00 a.m.–2:00 p.m.) of the UAE helped to specify more reasonable times for the tests. Standard dates could be sufficient to establish performance observation through the year, especially for North orientation since diffuse light is uniform and its pattern of variation is somewhat consistent and predictable. Hence, it was reasonable to select the standard Winter Solstice (21 December) and Spring Equinox (21 March). Because the Fall Equinox (21 September) would give similar results to the Spring Equinox (21 March), due to the symmetrical motion of the Sun around 21 June (also 21 December), only one of the equinoxes was used (i.e. Spring Equinox), and there was no need to simulate the Summer Solstice (21 June) because classrooms do not usually run during the summer.

Simulation

The study depended on computer simulation using Desktop Radiance [12]. Desktop Radiance is an accurate ray-tracing simulation software developed by the Building Technologies Department of the Environmental Energy Technologies Division at the Lawrence National Berkeley Laboratory. The simulation runs were performed for a standard classroom prototype in the UAE in two stages. The objective of the first stage was to identify the most critical viewer points (i.e. desk positions) and the most critical times for camera simulation. These are needed in the second stage for performing further and more detailed analysis. The objective of the second stage was to reveal any potential visual problems, from the chosen desk position (in stage 1), based on acceptable levels of luminance ratios within the field of view. The analysis was performed for different orientations and for different critical dates and hours. Finally, the last stage involved analysis of simulation results and drawing conclusions.

RESULTS AND DISCUSSION

Design analysis

The design information of the classrooms for the seven standard school prototypes was obtained from their architectural drawings. As shown in Table 3, it includes the depth, length, height, floor area, external wall area and glazing area. To what extent these designs agree with the target values, specified by previous research findings and rules of thumb (as described in Section 3), can be known from Table 4. The top row of Table 4 shows the recommended target values for the classroom depth (4.6 m), the ratio of height to depth (1:2, maximum), the proportion of the glazing area to the external wall area (20%), the proportion of the glazing area to the floor area (20%), the orientation (North) and the daylighting direction (from left side). Each gray cell in Table 4 indicates a problem with one of the mentioned design parameters. All seven prototypes do not have problems with the ratio of height to depth (1:2, maximum) and the proportion of the glazing area to the external wall area (20%); yet, all of them except School 3 has problems with the proportion of the glazing area to the floor area (20%), the orientation (North) and the daylighting direction (from left side).

Table 3.

Design information of classrooms from seven standard school prototypes.

Case study Depth Length Height Floor area Wall area Glass area 
School 1 4.80 10.64 3.60 51.05 38.29 8.93 
School 2 6.00 6.57 3.60 39.44 23.66 5.52 
School 3 6.00 9.71 3.60 58.28 34.97 8.16 
School 4 6.00 4.40 3.60 26.40 15.84 3.70 
School 5 5.25 9.72 3.60 51.02 34.99 8.16 
School 6 5.50 9.28 3.60 51.04 33.41 7.80 
School 7 6.00 8.51 3.60 51.04 30.62 7.15 
Case study Depth Length Height Floor area Wall area Glass area 
School 1 4.80 10.64 3.60 51.05 38.29 8.93 
School 2 6.00 6.57 3.60 39.44 23.66 5.52 
School 3 6.00 9.71 3.60 58.28 34.97 8.16 
School 4 6.00 4.40 3.60 26.40 15.84 3.70 
School 5 5.25 9.72 3.60 51.02 34.99 8.16 
School 6 5.50 9.28 3.60 51.04 33.41 7.80 
School 7 6.00 8.51 3.60 51.04 30.62 7.15 
Table 4.

Agreement of classroom designs with rules of thumb.

graphic 
graphic 

aD/H, classroom depth/height; bG/W, window glass area/wall area; cG/F, window glass area/floor area.

Shaded cells indicate values different from those recommended by the rules of thumb (shown above).

Identifying severe conditions

This process started by identifying the most critical viewer point, as described in Section 3.2. The luminance levels in the fields of view for viewer points A, B and C were investigated using camera simulation based on 21 March, 10:00 a.m. time. Table 5 shows these levels at horizontal view angles of 0°, 5°, 15°, 25°, 35° and 45°. These are measured from the visual axis toward the left and right directions. Table 5 also shows the recommended luminance levels (in column 1 of Table 5) at these view angles as benchmarks for performance evaluation. On the basis of the results, point B was found to be more problematic than the other points; accordingly, it was considered as the most critical viewer point (or desk position) and chosen for the other upcoming tests.

Table 5.

Acceptable luminance levels and those in the field of view for a standard classroom.

Acceptable luminance levels (cd/m2) [1View angle 
2500 L45 1982 1973 43 
1800 L35 1930 1983 1767 
1250 L25 1705 1938 1834 
850 L15 960 1943 1821 
580 L5 132 120 123 
580 Center 746 827 414 
580 R5 757 799 356 
850 R15 801 749 304 
1250 R25 65 61 275 
1800 R35 96 106 254 
2500 R45 103 101 246 
Acceptable luminance levels (cd/m2) [1View angle 
2500 L45 1982 1973 43 
1800 L35 1930 1983 1767 
1250 L25 1705 1938 1834 
850 L15 960 1943 1821 
580 L5 132 120 123 
580 Center 746 827 414 
580 R5 757 799 356 
850 R15 801 749 304 
1250 R25 65 61 275 
1800 R35 96 106 254 
2500 R45 103 101 246 

Shaded cells indicate values exceeding the acceptable luminance levels.

Identifying the critical times (dates and hours) was based on the need of solving visual quality issues resulted from the acute brightness coming from the windows and penetration of the direct sunlight into the classroom during severe visual conditions (i.e. critical times for different orientations based on the identified critical viewpoint). These severe conditions were determined based on camera simulation of the field of view. It was based initially on four selected hours for camera simulation runs: 8:00 a.m., 10:00 a.m., 12:00 p.m. and 2:00 p.m. Yet, the 2:00 p.m. was excluded for the east orientation classroom case and the 8:00 a.m. was excluded for the west orientation classroom case. They were judged to be less critical times due to the absence of direct sunlight at these hours (which depends on the sun position with regard to orientation and time). The produced images from the camera simulation of point B are shown in Figure 3. These simulation images reveal problems based on luminance levels in the filed of view such as the existence of direct sunlight impinging on the whiteboard or students' desks and acute brightness coming from the windows. The cases that are indicated with black dots are the ones that have severe conditions and definitely require improvements.

Figure 3.

Camera simulation of a critical field of view for the East, South and West orientations. Base cases on 21 December/21 March at different hours, with severe cases indicated by single black (less severe) or double black (more severe) dots.

Figure 3.

Camera simulation of a critical field of view for the East, South and West orientations. Base cases on 21 December/21 March at different hours, with severe cases indicated by single black (less severe) or double black (more severe) dots.

Luminance ratios analysis

The severe conditions that were identified earlier were used to simulate the luminance levels within the field of view. The cases are analyzed based on acceptable levels of luminance ratios within the field of view (Figure 4). The North orientation on 21 December at 12:00 p.m. case showed no problem in contrasting luminance levels between the task (150–250 cd/m2 on the whiteboard) and the darker surroundings (50–150 cd/m2 on the front wall); the acceptable ratio is 3:1. It also showed no problem between the task and the remote darker surfaces (37 cd/m2, on the left side wall); the acceptable ratio is 10:1. However, it showed problems between light sources (2008 cd/m2 on the windows) and surroundings (50 cd/m2, on the left side wall); the acceptable ratio is 20:1; and of the maximum contrast; the acceptable ratio is 40:1.

Figure 4.

Iso-contours and false color images produced from camera simulations (viewer point B) for different timing.

Figure 4.

Iso-contours and false color images produced from camera simulations (viewer point B) for different timing.

The East orientation on 21 March at 8:00 a.m. showed no problem between task (450–550 cd/m2) and darker surrounding (250-350 cd/m2); the acceptable ratio is 3:1. However, it showed problems between task (450–550 cd/m2) and remote darker surfaces (50 cd/m2, on the left side wall); the acceptable ratio is 10:1; between light sources (7233 cd/m2 on the windows) and surroundings (50 cd/m2, on the left side wall); the acceptable ratio is 20:1, and of the maximum contrast; the acceptable ratio is 40:1. The South orientation on 21 December at 10:00 a.m. and the West orientation on 21 March at 2:00 p.m. showed problems with all benchmarks for acceptable levels of luminance ratios within the field of view, as can be seen in Figure 4.

Mitigating the problems

Solar shading, protection from glare and redirection of daylight are three major functions in daylighting systems. In order to create acceptable interior conditions, windows need to be protected from glare and solar shading. The redirection of daylight can save energy, but it will add extra costs to construct it. The impact of daylighting systems on the view (to the outside) needs to be considered carefully. Interior systems are much less expensive than exterior systems, but they have only a limited solar shading effect. Exterior daylighting systems are usually costly because they have to be constructed to resist all weather conditions. In the harsh hot climate of the UAE, exterior daylighting systems must be able to resist the following conditions: Moveable exterior systems require a lot of maintenance and often collect dust; hence, they are not recommended for a highly dusty region like the UAE. Systems located in the cavity of the glass or within a double facade can be applied as part of an advanced ventilation strategy. They should be applied carefully due to the increased areas of glass and the highly admitted solar radiation, which could affect occupants' thermal comfort and construction costs.

  1. high levels of solar radiation, which affects all areas of the UAE, especially those located in the inland desert like Al-Ain city;

  2. high levels of air temperature, which affects all areas of the UAE;

  3. high levels of humidity, which affects the coastal areas like Abu Dhabi and Dubai cities.

  4. excessive dust carried by wind, which affects all areas of the UAE.

Schools in the UAE should be designed for solar shading and daylighting. Although reducing high levels of cooling loads should be a significant driving force, students comfort, productivity and learning are other important factors. Some systems such as overhangs, sun shades and fins are useful for solar shading, but they do not control glare; therefore, another system that controls glare needs to be added to make these design solutions work. A light shelf combines solar shading and sunlight redirection, improving the distribution of daylight and allowing a view through the lower part of the window [13]. In sunny low-latitude countries like the UAE, the light shelf can protect areas near the window from direct sunlight with only a slight reduction in light levels throughout the rest of the room. To reduce cooling loads and solar gain, an exterior light shelf is the best compromise between shading requirements and daylight distribution [13]. New advanced daylighting systems in combination with advanced controls can bring daylight deep into a space and reduce cooling loads relative to those experienced with artificial lighting. Tracking systems can be used to regulate daylight levels and reduce thermal loads [13]. The use of skylights (with horizontal glass) in the UAE is not recommended due to high altitude angles of the sun rays in the summer that can penetrate easily through horizontal glass causing glare and excessive heat. Top lighting systems with vertical glass such as clerestories and roof monitors are more suitable for hot climates. Detailed description of the characteristics of advanced daylighting systems to aid building professionals in choosing a system can be found in the literature [13].

Sunlight can also be filtered and softened by trees or by devices such as trellises and screens. These natural methods (i.e. plants and trees) provide better quality of daylight than the use of light drapes or translucent glazing because of the problem of glare. They are highly recommended for very hot climates like the UAE. In addition to improvements in lighting environments, plants and vegetation can provide other environmental benefits: create a better microclimate in courtyards and outdoor spaces with the modified thermal conditions as a result of shading and passive cooling; provide esthetics in the indoor and outdoor spaces; reduce noise levels; provide healthier spaces and filter air from dust and unhealthy particles; and improve thermal and visual comfort and improve well being.

CONCLUSIONS

The design information and site visits analysis of standard classrooms in the UAE have revealed several design issues that affect the daylighting environment and visual quality inside classrooms. These were the classroom depth (>4.6 m), the proportion of the glazing area to the floor area (>20%), the orientation (mostly not North) and the daylighting direction (mostly not from the left side). The site visits supported these findings. The simulation runs showed three important problems that caused the visual discomfort: acute contrasting luminance between the task surface (i.e. whiteboard) and other near surfaces, high brightness coming from the windows and uneven distribution of daylight in the space. The sitting location of the student is an important factor and has significant impact on visual quality. On the basis of camera simulation and acceptable luminance levels, viewer point B (in the rear, opposite side of the windows) was found to be more problematic than the other viewer points (i.e. A and C); accordingly, it was chosen as the most critical viewer point (or desk position). South windows experience direct sunlight for most school hours (8 a.m.–2 p.m.) in the winter when the sun is in low altitude angles. This problem is easier in the other seasons. East windows experience direct sunlight in the early morning hours (8–10 a.m.) and west windows experience direct sunlight in the afternoon hours (1–2 p.m.). The North orientation on 21 December at 12:00 p.m. did not meet the requirement for the acceptable luminance ratios between light sources and surroundings (i.e. 20:1) and of the maximum contrast (i.e. 40:1). The East orientation on 21 March at 8:00 a.m. did not meet the requirement for the acceptable luminance ratios between task and remote darker surfaces (i.e. 10:1), between light sources and surroundings (i.e. 20:1) and of the maximum contrast (i.e. 40:1). The South orientation on 21 December at 10:00 a.m. and the West orientation on 21 March at 2:00 p.m. did not meet any of the requirements for the acceptable luminance ratios for all levels in the field of view. Mitigation of the problems was discussed based on three major functions of daylighting systems (i.e. solar shading, protection from glare and redirection of daylight) and design requirements of the UAE climate.

ACKNOWLEDGEMENT

This work was supported by funds from Research Affairs at the UAE University under research project 06-03-7-11/06.

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