Iyad Beaini-Daylight Experiment

University of Westminster, school of Architecture and Cities Department of Architecture and Interiors Fundamentals of Environment Design 2020/21 Fundamentals of Environment Design: Laboratory Report Daylight Experiment

Iyad El Beaini April 2021

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Table of content

I take this opportunity to thank my tutor Dr. Joan Vallejo and Zhenzhou Weng for their guidance and support throughout the module. I express our gratitude for their assistance, encouragement, and valuable inputs for my paper project to be successful through the previous tutorials.

A special thanks to our guests and visit lecturers for providing us with the needed references to understand and compare the results tackled. This allowed me to gain a deep understanding of daylight and its effect on illuminating the space, and have a general knowledge about the all the other topics.

This topic helped a lot to understand my environment and my daily life in different weather conditions. Also it allows me to notice the small details of the illuminance distribution in a small space with only one opening as a source of light. Due to the papers suggested by my tutors and the guiding lectures presented in Tuesday classes, in addition to the last optional tutorial. I can clearly understand the importance of daylight in building performance.

I am thankful and fortunate enough to get constant encouragement, support, and guidance from all the teaching staff of the Architecture and Environmental Design course during the COVID-19 pandemic to conduct the classes online without which my paper work would not have completed successfully.

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In the Fundamentals of Architecture and Interior course taught in the university of Westminster-Marylebone, five main experiments were introduced in the workshop sessions for the student to replicate: Natural ventilation, evaporative cooling, thermal mass, acoustics and daylight. All these experiments were done previously by the tutors, and recorded for the student to analyze the principle and the idea behind the experiment replication. In the other hand, daylight is an important factor for architects and designers to understand before designing or analyzing a new project. It’s one of the most important criteria to achieve a better environmental performance for any building all around the world.

In this report we will tackle the objective and hypothesis of the daylight experiment to elaborate the theoretical ground behind it, followed by the methodology where a detailed explanation of the two experienced tasks will take place, and illustrated with images took while doing the experiment or other materials to verify the results. After that, all the material and equipment used will be listed to conduct the experiment. At the end, the result will be described and interpreted followed by the final conclusion.

The purpose of the daylight experiment is to demonstrate the understanding of the physics around daylighting. The experiment is a replication of two different tasks, each task will be explained and tackled separately.

Task-A: Illuminance mapping: A physical room model, with different opening sizes, will be tested, analyzed and compared to a similar digital model built in Andrew Marsh’s daylighting website application (fig.1) to study, compare, and conclude the best daylight factor, in three different opening sizes.

Task-B: HDR luminance analysis: A specific location in the reference room, will be tested by a phone camera to understand the quantity of luminance received by this surface and to point the glare source there. According to false colored images and different shutter speeds.

The experiments will happen in the occupant living room. In two different weather conditions, a sunny and a cloudy day. Each weather condition will be used in one of the tasks examined for a better understanding of the illuminance distribution in the studied location.

Fig.1 picture of the physical model of task-A vs task-B experiment

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A- Principle of light For us to understand more the principles of light, Dalton et al (2015) (fig.2) explained that source of light output luminous energy (lumens). This energy reaches a space by an intensity measured in candelas, and varies according to the source of light itself (fig.2). When the luminous intensity reaches a surface, it becomes illuminance (Lux= lumens/m2), and the naked eye receives it as Luminance (candelas/m2). In the task A of the workshop, the illuminance on the surface is the studied component. Taking into consideration the sky and the outdoor conditions. Looking from the window where the experiment will take place, three main components should be looked at: (fig.3) sky component (SC): is the direct light from the sky to the window. And the vertical sky component VSC-is the angle created between the visible sky and the window tested. In both experiment have an angle of 90 degree. In the task A, overcast sky was the ideal sky condition for the sun’s luminous energy to be received equally from all the direction, the experiment took place at 12 pm in a cloudy day in 15 April with an unobstructed sky illuminance between 16247-8083 Lux, while this number is low compared to the average of illuminance in April at 12pm in the weather file data of London (Fig.4&5). In the other hand, and for the Task B, a clear sky condition was tested to study the glare source and the intensity with an unobstructed sky illuminance of 19059 Lux

Fig.2 Illustration of the principle of light and luminance intensity by from Dalton (2015) and LightingEver (2015) respectively

Fig.3 illustration of all the sky component received inside- form ZNEP book (2016)

Overcast sky condition

clear sky condition

Fig.4 International commission on illuminationAndrew March’s webisée (2018)

External reflected component (ERC): the workshop was done on the medium obstructed window of the referenced living room, where the bright colored context buildings produce a high reflected component, with a high Albedo value on the experiment location. The ERC in the studied case may develop visual discomfort.

Internal reflected component (IRC): the replicated model for Task-A, will have a white interior, so the reflected component will reach a high value. And an Average of interior LRV-light reflectance value was equal or bigger than 0.7579

Fig.5 Daily average diffuse illuminance-London weather file

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B- Daylight factor-DF

“The daylight factor is the illuminance received at a point indoors, from a sky of known or assumed luminance distribution, expressed as a percentage of the horizontal illuminance outdoors from an unobstructed hemisphere of the same sky. direct sun light is excluded form both values of illuminance” (page 87 LG10: Daylighting- a guide for designers.)

The manual calculation of the average daylight factor can be done in two different ways, in this study they will be called ‘Average Manual calculated’ and ‘Average Formula calculated’ respectively: Fig.6 section of the two component of the average manual calculated daylight factorRandall & Jacot, (2002)

DF= (Ein/ Eout) x 100% When (Ein ) is the internal illuminance and (Eout) is the unobstructed external illuminance (fig.6). Also, daylight factor can be expressed by the formula below:

Average DF =

𝑻 × 𝑨𝒘 × 𝜽 × 𝑴 𝑨 × 𝟏 − 𝑹𝟐

When (T) refer to the visible transmittance of glazing, (Aw) refer to the total area of glazing, ( 𝜽) refer to the visible sky angle on the window, (M) refer to the maintenance factor that depend on the cleaning, (A) refer to the total area of the interior surface, and ( R) refer to the Average of light reflectance value- LRV of the interior surface(fig.7). The LRV is expressed by:

𝑹=

Fig.7 Illustration and annotation of all the DF component –week 7 daylighting presentation

𝑹𝒘𝒂𝒍𝒍 × 𝑨𝒘𝒂𝒍𝒍 (𝒆𝒙𝒄𝒍𝒖𝒅𝒆 𝒘𝒊𝒏𝒅𝒐𝒘) + 𝑹𝒄𝒆𝒊𝒍𝒊𝒏𝒈 × 𝑨𝒄𝒆𝒊𝒍𝒊𝒏𝒈 + 𝑹𝒇𝒍𝒐𝒐𝒓 × 𝑨𝒇𝒍𝒐𝒐𝒓 + 𝑹𝒘𝒊𝒏𝒅𝒐𝒘 × 𝑨𝒘𝒊𝒏𝒅𝒐𝒘 𝑨

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Taking the occupant living room as reference for our replicated workshop, it’s a 370x355 cm room with 250cm ceiling height, the room has one standard sized window on the north orientation as the only source of light there (fig.8) (fig.10). The occupant suffers from daylight comfortability (fig.9). Taking into consideration that the space is north oriented, the space is well daylit in sunny days and in direct global illuminance, and sometimes glare took place, due to the high externally reflected component -ERC- found in the opposite building, while the space is weakly daylit in overcast sky conditions. This contradiction led to taking the daylight analysis seriously and the occupant decided to understand more what was happening and the influence of other opening dimensions on the space.

So, in this report, the daylight experiment will be replicated in the two tasks, to understand how light will be distributed and reflected in a room with only one source of light. The two tasks took place in two different days (14-15 April, 2021) with two different weather conditions.

Fig.8 picture taken by the occupant of the replicated physical model scale 1/100- interior

The purpose of the two experiment is: 1. Identify the major effect of the opening size, using the same window orientation, on the daylight factor of the physical model.

2. Identify which factor may cause the inaccuracy between the digital and the physical model result.

3. Verify the importance of blinds to reduce glare effect.

Fig.9 picture taken by the occupant in the studied area

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Theoretical ground:

The room has a north oriented source of light, the Average daylight factor should not reach high percentages, with its small window to wall ratio, since the sun hits the room from the back. The room needs a bigger window for better illuminance inside, especially in cloudy sky conditions. But since the occupant experiences glare in the existing scenario, a bigger window will increase the risk of glare in sunny days.

Finally, a bigger window with a controlled interior blind may be the right decision for such a case.

Fig.10 picture taken by the occupant of the replicated physical model scale 1/100- exterior

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50% bigger window dimensions

Existing window dimensions

50% smaller window dimensions

To verify the theoretical vision for the best scenario, two different experiments took place, named as task-A and task-B, this chapter will elaborate the methodology of the two experiments in detail. Starting with: Task-A: Illuminance mapping: to replicate the room correctly, all the actual room dimensions were taken. A 1:100 scale physical model was built in a simplified way(fig.10), with the existing window size (13x13 cm)(fig.8) and a light transmission of 100%, for a future reference of (T=1) (fig.8). Two additional window sizes were created, one of them bigger then the original one with 50% additional opening size, and the other is 50% smaller. All the windows have the same conditions to test the difference Daylight factor and the illuminance inside the physical model (fig.11). The windows were named “window 1”, “window 2”, and “window 3” with a window to wall ratio of 9.6%, 17.7%, and 26% respectively. The interior part of the model was covered by white paper for having the same IRC reference in each case tested. Since the model is not perfectly covered by the white papers and small gaps may be found between the intersection of the walls, the maintenance factor was decided to be (M=0.95). Moreover, due to the wide spacing between the experiment location and the facing building, compared to the window size of the physical model, the visible sky angle of the window was referred to as (90o). The ground of the box was divided into a grid of 9 small boxes with a cross in the middle of each one (fig.13). All the light infiltration was fixed, aiming to have only the window as a source of light. Beside all of that, a small window opening was created on the East elevation, for spotting the measured number without obstructing the illuminance form the main window while doing that (fig.13). On the other hand, a similar model, with the same dimension, was built on Andrew Marsh’s Dynamic Daylighting web app (fig.12) and a digital daylight factor was calculated by the system immediately.

Fig.11 picture taken by the occupant of the three different window sizes

Fig.12 screenshot of the model built in Andrew Marsh’s Dynamic Daylighting web

Phone stand of 9 cm height Grid for measurement reference Small window for result observation Fig.13 picture taken by the occupant of interior of 9 the model

It was a cloudy day, the box was placed on the north elevation window, the window was open to get an unobstructed sky visibility, and the experiment began(fig.14).

First of all, the unobstructed sky illuminance was measured, using a phone application and the device was directed upward. The result was written down. Then, the illuminance level was tested for the existing scenario using the same application.

Window 1 and 2 was removed while window 3 remains in place. The phone was placed on an elevated element to reach 9cm over the model ground, for it to be on the same level with the window opening(fig.13) and the phone sensor(fig.15) was spotted over the middle cross of each box. After writing down the measurement observed from the small window, the phone will be moved to the second cross and the experiment will be repeated for all the 9 boxes there.

Succeeding taking all the measurements of the first experiment, all the result was illustrated in a colored grid. The ‘Average Manual calculated’ formula was applied to know the percentage DF of each box referring to the outdoor sky illuminance measurement. All the percentages will be added together and divided with the number of measurements taken, the result obtained will be the Average Manual calculated DF of this studied case. The uniformity ratio can be calculated after obtaining the average DF, when dividing the smallest daylight factor obtained by the total average.

Fig.14 picture taken by the occupant while doing the experiment.

Illuminance sensor

Finally, to insure the result, the ‘Average Formula calculated’ daylight factor will be calculated, using the current scenario glazing area as (Aw) and the average interior-LRV- with the internal reflected component-IRC=0.9.

If all the average daylight factors obtained were close to each other, that means the experiment was done successfully. And the experiment will be repeated over the two different window sizes to analyze the result in the next part.

Fig.15 picture of the phone used in the experiment-Samsung Note 8- and the sensor location

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Luminance analysis: Aiming to spot the reflection and the glare effect happened in the sunny days, the camera stand was set on the floor next to the working desk, it was calibrated and set in the room corner ( fig.16), ready to be used. On the other hand, an application called “Fusion Optix” was installed on the phone to do the experiment. The application specs will be found in the next chapter.

First off all, an HDR image was taken by the normal phone camera, the frame spotted had the laptop in. It was turned on and the daylight colorful presentation appeared on the screen. Moreover, a big part of the closed window was also spotted in the picture. In addition to the white reflective table. Adding to all of that, the door of the kitchen was left open, because the occupant was aiming to replicate the daily life scenario in the experiment (fig.17). And the experiment begins.

On the application, the ISO was fixed and the shutter speed was the changeable input there. Four different photos were taken in each scenario with 1/4000s, 1/1000s, 1/250s, and 1/60s shutter speed respectively.

The experiment was repeated in three different scenarios, the first scenario applied was with the blind off, the second one when we put the blinds on but not fully closed and the final one when all the blind part is closed. The aim of the blind application is to decrease the illuminance inside.

Fig.16 picture of the camera stand, calibrated and ready for the experiment.

Blind used of 0%

Blind used of 60%

Blind used of 90%

Fig.17 HDR images from the same location, of the three different tested scenario

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Different materials and equipment were used in both experiments, in task-A more materials were found since a physical model was built, in addition to the website application inputs and a phone application used. While in task-B a phone application and few shots summarized the whole experiment.

Starting with task-A. First of all, to do the physical model, a cardboard delivery package of 39x59 cm was modified to suit the experiment, white A3 papers were used to cover the inside of the box. A cutter and a scissors, were the only tools to cut the materials into their needed dimensions. Moreover, glue and scotch were used to attach elements together. Highlighters took place Also, to differ the opening tested. A pen to illustrate the grid on the ground and to numerate the opening tested. And finally, a meter to take all the measurements (fig.18).

Fig.18 All material used for task-A

Beside the physical model, a phone application was used too. Lux light meter- phone application, was the helpful tool to measure the illuminance of each grid point (fig. 19). Finally, a digital calculator was part of the experiment, to do all the manual/formula calculations (fig.18).

On the other hand, as mentioned before, a similar digital model was built on Andrew Marsh’s Dynamic Daylighting website application in each scenario for a result comparison at the end (fig.20).

Fig.20 Andrew Marsh’s Dynamic Daylighting website application

Fig.19 Phone application-Lux Light Meter-google image

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Going into task-B. the equipment in this experiment are few and three main equipment or materials was used there. Starting with the camera stand, for a better calibration and a similar frame.

A phone camera was used in this experiment, alongside with Fusion Optix- phone application to get the group of false colour luminance images (fig.21-22-23).

Fig.21 Samsung note 8 -back camera

Fig.22 FUSION OPTIX application instructions

phone

Fig.23 professional camera stand with a manual phone stand

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Andrew Marsh’s Dynamic Daylighting website- Average DF result

Manually calculated and measured- Average DF result

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Window to wall ratio

9.6%

Window to wall ratio

17.7%

Window to wall ratio

26%

Window size

0.07x0.13m

Window size

0.13x0.13m

Window size

0.19x0.13m

Room size

0.36x0.38x0.25m

Room size

0.36x0.38x0.25m

Room size

0.36x0.38x0.25m

LRV

0.7794

LRV

0.7688

LRV

0.7579

Formula calculated average DF

2.98%

Formula calculated average DF

5.32%

Formula calculated average DF 7.81%

Website Measured average DF

3.59%

Website Measured average DF

6.76%

Website Measured average DF 9.88%

Manual calculated average DF

3.91%

Manual calculated average DF

7.81%

Manual calculated average DF

11.1%

Uniformity ratio

0.4

Uniformity ratio

0.38

Uniformity ratio

0.51

Unobstructed sky illuminance

11060 Lux

Unobstructed sky illuminance

15247 Lux

Unobstructed sky illuminance

8083 Lux

Sky condition

cloudy

Sky condition

cloudy

Sky condition

cloudy

Fig.26 Average DF obtained in three different test types- 50% smaller window size

Fig.27 Average DF obtained in three different test types- existing window size

Fig.28 Average DF obtained in three different test types- 50% bigger window size

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First of all, a small window, with a window to wall ratio of 9.6%, was applied to the physical model and the result shows that all the Average daylight factor calculated and obtained was close to each other and scored a low score that is unacceptable compared to CIBSE requirements (fig.24&25). In the measuring part of the experiment a lack of daylight was obtained in the place, the illuminance next to the window reached the maximum daylight factor of 11.5%, or a 1278Lux from an unobstructed sky of 11060Lux, which may be acceptable but not enough since a big part of the room had an Average daylight factor less than 2.5%, or in other words less than 250 lux in same sky condition. and similar numbers require artificial light in the majority of the time. In Andrew Marsh’s Dynamic Daylighting website application, the measured average can reach in its worst case a 1.95%, which is very low. Or 29.16% which might be acceptable (fig.26).

The uniformity ratio in his case was: 0.4, which means that is the distribution of illuminance in the room was acceptable

Fig.25 BS EN 12464-1-2011 Light and lighting — Lighting of work places Part 1 Indoor work places

Fig.24 paragraph of the minimum DF required interior- CIBSE guide A

Andrew Marsh’s Dynamic Daylighting website- Average DF result

Starting with task-A, the experiment was tested in three different windows sizes. The occupant thought about studying two different scenarios beside the existing one to see its performance on the room illuminance.

Manually calculated and measured- Average DF result

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Using all those materials and equipment, each experiment took place in different scenarios.

Window to wall ratio

9.6%

Window size

0.07x0.13m

Room size

0.36x0.38x0.25m

LRV

0.7794

Formula calculated average DF

2.98%

Website Measured average DF

3.59%

Manual calculated average DF

3.91%

Uniformity ratio

0.4

Unobstructed sky illuminance

11060 Lux

Sky condition

cloudy

Fig.26 Average DF obtained in three different test types- 50% smaller window size

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Secondly, the existing window, with a window to wall ratio of 17.7%, was tested in the physical model as well, and the result shows that the average daylight factor reached in all the experiments done for this window size, are also close to each other with a max gap of 2.49% (fig.27) they vary between 5.32% and 6.76%.

Moreover, the obtained results were acceptable referred to CIBSE guidance, that requires more than 5% as minimum value (fig.24&25).

Moreover, In the measuring part of the experiment, and especially next to the window, a high percentage of 26.6% was obtained, or 4100 lux out of 15247 Lux, was measured. That value is a comfortable result for a north oriented window, glare may happen in some hours of the day, but still a better result than the previous one. But tackling the back of the room, the Average daylight factor in around 3% and reach a 487 Lux as maximum value, which is reaching the lighting requirement of the workplace (fig.24&25).

Manually calculated and measured- Average DF result

The uniformity ratio in his case was: 0.38

Andrew Marsh’s Dynamic Daylighting website- Average DF result

Fig.25 BS EN 12464-1-2011 Light and lighting — Lighting of work places Part 1 Indoor work places

Fig.24 paragraph of the minimum DF required interior- CIBSE guide A

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Window to wall ratio

17.7%

Window size

0.13x0.13m

Room size

0.36x0.38x0.25m

LRV

0.7688

Formula calculated average DF

5.32%

Website Measured average DF

6.76%

Manual calculated average DF

7.81%

Uniformity ratio

0.38

Unobstructed sky illuminance

15247 Lux

Sky condition

cloudy

Fig.27 Average DF obtained in three different test types- existing window size

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From all those experiments we can clearly observe that the first scenario is not performing well, and every time we apply a bigger window we can clearly see the improvement in the illuminance and daylight factor inside.

Manually calculated and measured- Average DF result

By far, the highest percentage obtained in the taskA experiment was in the third tested window size, by a window to wall ratio of 26%. The result shows that all the averages of daylight factors were close to each other, and the best performance happened next to the wide window, for 33.7%, or 2724lux out of 8083lux (fig.28). referring to CIBSE all the measurement of daylight factor reached in this room was over the minimum requirement by CIBSE (fig.24&25). Next to the window, a higher possibility of glare may take place, but in the back no artificial light is needed since all the results are comfortable for exercises done there.

Fig.24 paragraph of the minimum DF required interior- CIBSE guide A

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Window to wall ratio

26%

Window size

0.19x0.13m

Room size

0.36x0.38x0.25m

LRV

0.7579

Formula calculated average DF 7.81% Website Measured average DF 9.88%

Andrew Marsh’s Dynamic Daylighting website- Average DF result

The uniformity ratio in his case was: 0.51

Fig.25 BS EN 12464-1-2011 Light and lighting — Lighting of work places Part 1 Indoor work places

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Manual calculated average DF

11.1%

Uniformity ratio

0.51

Unobstructed sky illuminance

8083 Lux

Sky condition

cloudy

Fig.28 Average DF obtained in three different test types- 50% bigger window size

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In this experiment, in a sunny day, normal HDR photos was taken, followed by false color illuminance pictures in different shutter speed, over three different scenarios (fig.29-30-31).

As a result, it’s clearly seen that when the shutter speed increases the picture became brighter and receive more luminance, because the scale changes and become smaller. From the different shutter speeds used, the 1/250s in the perfect reference for the occupant to experience and spot glare source. The experience happened over a clear window without blind and the glare can be spotted coming from outside with a big amount. In addition to the reflection happened on the screen of the laptop (fig.29). Blinds was used in the second experiment with a 60% closeness. The glare amount decreases a lot and the reflection on the screen become neglected (fig.30). Blinds was fully closed in the final experiment, and there are no big changes happened. In the other hand the place became dimmer, as the occupant stated (fig.31).

ISO fix-

shutter speed: 1/4000

ISO fix-

shutter speed: 1/1000

ISO fix-

shutter speed: 1/250

ISO fix-

shutter speed: 1/60 Fig.29 HDR image and a group of false colour luminance images with different speed shutter- clear window

Fig.30 HDR image and a group of false colour luminance images with different speed shutter- blinds 60% on

Fig.31 HDR image and a group of false colour luminance images with different speed shutter- blinds 90% on

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After looking over the 1/250s shutter speed, luminance ratio took place and a small and a wide frame were spotted to analyze and guess the adjacent and the non-adjacent luminance ratio, taking into consideration that it should not exceed 3:1 for the small frame and 10:1 for the bigger one (IESNA, 2000).

Starting with the window without blinds, glare and visual discomfort was spotted clearly coming from the direct sky illuminance and from the reflected element of the context building. The illuminance ratio was in the acceptable range, it reached 4:1 in the wide frame and 3:1 in the small one. But the occupant is unsatisfied with the computer screen reflection.

On the other side, when blinds are used but not fully, the total amount of illuminance decreased, and the screen reflection became neglected. The luminance ratio remains in the wider frame as in the previous scenario, and decreases in the smaller one to become 2:1. These values show a better illuminance performance with a better visual comfort and less glare inside.

comfortable

Finally, we tested the same experiment over totally closed blinds, the space became dimmer and since there is no external light the screen illuminance became the brighter element in the room. In terms of luminance ratio, the value reached, in the wide frame, is less than the previous scenarios.

The two ratios became closer to each other due to the absence of natural light inside.

Luminance ratio non-adjacent surfaces = 200 cd/m² : 50 cd/m² = 4:1

comfortable

adjacent surfaces = 150 cd/m² : 50 cd/m² = 3:1

Luminance ratio non-adjacent surfaces = 170 cd/m² : 40 cd/m² = 4:1 adjacent surfaces = 100 cd/m² : 40 cd/m² = 2:1

Un-comfortable

Luminance ratio non-adjacent surfaces = 150 cd/m² : 50 cd/m² = 3:1

adjacent surfaces = 100 cd/m² : 50 cd/m² = 2:1

Fig.32 the luminance ratios for the three different scenario with 1/250s speed

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In task-A, the result obtained shows that the space requires better illuminance due to its orientation, and specially in overcast sky conditions.

In terms of illuminance values, the smaller window does not perform well, while the other two perform way better in terms of daylight factor. The existing scenario reaches the required values and specially in the back of the room but these values might be insufficient since the occupant is complaining about the illuminance there, and he always requires artificial light.

In terms of Illuminance, the third scenario with a 50% bigger window size is the best performer, and reaches the highest values. These results might be perfect for the back of the room but glare can be felt next to the window in such scenarios.

Finally, the average daylight factor calculated and optioned was not identical since al lot of factors may affect the result, like the unstable sky illuminance obtained in the experiment period and the inaccuracy of the application used in the experiment. Also the reflection of the context plays an important role in the accuracy of the result. Adding to all of that, the different thicknesses of the walls and the light infiltration of the materials used in the physical model.

Tackling the room size, since the uniformity ratio is low and scored in worst scenario 0.51, that means that the room have no issues in depth compared to the opening size.

On the other hand, the task-B was done in sunny day and in the 1/250s shutter speed, glare can be found in the existing scenario, where the blinds are not in use, the space experience glare and it is spotted from the external sky directly, in addition to the reflected white painting of the context building. When blinds are down but not fully closed, the glare effect decreases a lot and the screen reflection starts to get neglected. Moreover, the screen illuminance is still less than the daylight factor of the room.

In the last scenario, when the blinds are fully down, glare cannot be felt anymore but the space became fully dim and the laptop screen became the light source, which is unhealthy for a longtime work.

To make the space brighter, especially on the north elevation, a bigger opening should take place or a bigger source of natural light should be installed, this scenario might create glare and bad reflection, especially next to the window.

To avoid glare, horizontal blinds should be installed and controlled from inside, for the occupant to control his own environments. The blinds might totally separate the interior from the exterior or open them together.

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• Fig.2: Dalton, A. (2015, October 9). Lumens for the laymen. Retrieved from RS Agencies: http://rsagencies.co.za/lumens-for-the-laymen/ • Fig.2: Lightingever. (2015, January 16). Luminous Intensity. Retrieved from Lightingever: https://www.lightingever.co.uk/blog/luminous-intensity/ • Fig.3: NZEB. (2016, August 12). Daylighting. Retrieved from Net Zero Energy Buildings: http://nzeb.in/knowledge-centre/passive-design/daylighting/ • Fig.6: Randall, J., & Jacot, J. (2002). The performance and modelling of 8 Photovoltaic materials under variable light intensity and spectra. World Renewable Energy Congress VII & Expo (pp. 18). Cologne: WREN. • Fig.7: week 7, daylighting presentation, fundamentals of Environmental Design_ Zhenzhou Weng • Fig.21-22-23: https://www.fusionoptix.com/smartphone/instructions/ • Fig.24: CIBSE. (2019). CIBSE Guide A: Environmental Design. London: CIBSE. • Fig.25: BSI. (2011). BS EN 12464-1:2011 Light and lighting — Lighting of work places Part 1 Indoor work places. London: BSI • IESNA. (2000). Chapter 11 Office Lighting. In IESNA, The IESNA Lighting Handbook. New York: IESNA. • Images taken by the occupants • Google search images

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