Thesis_Chen Hu

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SIMULATION ON EFFECTIVE
DYNAMIC SKYLIGHT
STRATEGIES
Chen Hu
Master of Science in Building Performance and Diagnostics
05/11/2015
Advisors
Erica Cochran, Flore Marion, Azizan Aziz, Vivian Loftness

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Contents
1. Abstract............................................................................................................................. 3
2. Introduction ...................................................................................................................... 4
2.1 Objectives ................................................................................................................................4
2.2 Hypothesis ...............................................................................................................................4
2.3 Deliverables .............................................................................................................................4
2.4 Methodology............................................................................................................................5
3. Background of U.S. Energy Consumption............................................................................ 8
4. Literature Reviews of Skylight Benefits ............................................................................ 11
5. Introduction of Daylighting Simulation Software.............................................................. 28
6. Dynamic Skylight Strategy Simulation and Energy Analysis............................................... 30
6.1 Pittsburgh Climate..................................................................................................................30
6.2 Autodesk Ecotect Model of Intelligent Workplace (IW) ............................................................35
6.3 Dynamic Skylight Shading Device ............................................................................................41
6.4 Skylight Material Hypothesis...................................................................................................42
6.5 Simulation Process..................................................................................................................43
6.5 Lighting Analysis of Dynamic Skylight System ..........................................................................47
6.5.1 Standards and Regulations ........................................................................................................47
6.5.2 Illuminance Level Analysis..........................................................................................................48
6.5.3 Glare Analysis.............................................................................................................................68
6.6 Recommendation on Dynamic Skylight Strategies....................................................................84
6.6.1 Dynamic Skylight Strategies Evaluation.....................................................................................84
6.6.2 Dynamic Skylight Strategies Schedule .......................................................................................94
8. Energy Benefit of Proposed Skylight Strategies................................................................. 98
9. Limitations .................................................................................................................... 101
10. Conclusion................................................................................................................... 102
11. Future Work ................................................................................................................ 103
12. Acknowledgement....................................................................................................... 104
13. Bibliography ................................................................................................................ 105
References ........................................................................................................................ 105
Appendix........................................................................................................................... 108

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1. Abstract
Currently, 73% of U.S. commercial buildings are under 10,000 square feet, which is considered as small
(less than 5,000 sf) or medium size (between 5,000 and 50,000 sf) buildings (EIA, Commercial Building
Energy Consumption Survey, 2014). The commercial building sector in the northeast region of the U.S.
accounts to 19.5% total commercial floor space and 21.4% total energy consumption. (Pei, 2013) It has
been estimated that buildings with no more than two floors take up to 64% of total building number and
60% of commercial floor space is directly under roof space. However, currently only 2% - 5% of the total
commercial building floor space has skylight installed. (Pei, 2013) This is a good opportunity for skylights
applications since skylight system is more efficient in these kind of buildings due to their high roof-wall
ratio. Properly designed and placed skylights can supply enough lighting for commercial buildings during
clear weathers without using additional artificial lights. For cloudy weather, skylights can still reduce
artificial lighting energy usage by supplying supplementary lighting. Researches also shows that skylight
systems can increase occupants’ productivity (Bristolite, 2013). Thus, increasing the number of studies
has been focused on efficient skylight system. This research is mainly concentrated on energy
conservation part of dynamic skylight strategies. The dynamic strategies in this thesis project refers to
the shading device type on skylight as not fixed, but adjustable in different times or under different
weather conditions. For example, the blinds panel position can be changed at different time during a
day (hourly schedule) or in different season (seasonal schedule). Venetian blinds are also replaced by
tensioned shades during summer (seasonal schedule). Many studies have been conducted on influence
of skylight on indoor environment analysis, however, there is few studies working on economic benefits
aspect of skylight system currently. The analysis of related return of investment (ROI) of different
skylight system is insufficient.
This thesis project focuses on software simulation of dynamic skylight strategies. Using Autodesk Ecotect
and Radiance, the daylighting condition of Intelligent Workplace (IW) of Carnegie Mellon University is
simulated. Three skylight strategy experiment groups are analyzed through simulation: controlled group
(no shading device), Retrosolar venetian blinds group, and Lutron tensioned shade group. Four different
blinds panel position is analyzed in this project as well, fully closed, fully opened, positive 45 degree, and
negative 45 degree. Glare analysis is also conducted. Cases related to daylighting simulation for heating
dominated areas similar to Pittsburgh are studied to provide methodology for energy conservation
analysis.
The comparison between venetian blinds and tensioned shades is conducted to give advice on skylight
shading device selection. The recommendation on dynamic skylight strategies is provided in both
seasonal schedule and hourly schedule.

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2. Introduction
2.1 Objectives
The objective of this study is to quantify skylight dynamic shading device system’s visual benefit in
humid continental climate (northeast U.S. region) through software simulation. The simulation results
are mainly for open plan office and climate similar to Pittsburgh, PA which is located in the IECC Climate
Zone 5. Besides, the methodology of the simulation can be replicated and used in other region for
further study. An literature review was also conducted to summarize the benefits of successful building
skylight cases and simulation methods for skylight evaluation. A filed experiment was conducted in
Intelligent Workplace of Carnegie Mellon University in 2014. This study can be considered as a following
and supplementary study of the previous study. The previous field only provide venetian blinds
schedule at one position. Since the previous field experiment on skylight shading device is still static
(one blinds panel position), this simulation can make skylight strategy dynamic. It can provide more
detailed skylight strategy schedule.
2.2 Hypothesis
The goal of this research is to identify if dynamic skylight can achieve the following benefits (or
improvements) utilizing computer software to simulate different shading configurations and weather
conditions:
1. The dynamic skylight system can improve indoor visual environment.
a. The dynamic skylight system can help reduce glare issue from daylight.
b. Different blinds panel positions have different ability on preventing glare.
c. Tensioned shades can help prevent from the most glare compared with other groups.
2. Different skylight strategies have different visual performance at different times of a day,
under different weather conditions, and in different seasons.
a. Dynamic skylights can allow maximum sunlight while maintain occupant visual comfort
within related standards.
b. Tensioned shades provide the best indoor visual performance in summer.
c. Different angles of blinds panel have totally different effect on indoor visual
performance.
d. Venetian blinds can fulfill most of visual requirement and are more convenient
compared with tensioned shades.
3. Dynamic skylight strategies can reduce energy consumption compared with normal skylight.
2.3 Deliverables
This thesis project will provide the following items as outcome deliverables

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1. Detailed analysis of skylight strategies used in Intelligent Workplace of Carnegie Mellon University.
Including product information, explanation of its benefits, and related case study on each type of
skylight strategies.
2. Detailed Ecotect simulation model of Intelligent Workplace (IW) of Carnegie Mellon University
3. Simulation results on light level and glare. This thesis project emphasizes on visual benefits of
dynamic skylight strategies since the previous study focuses on thermal comfort.
4. Seasonal and daily skylight strategy using schedule based on simulation result. The schedule is
provided as a combination of considering light level and glare analysis.
5. Energy simulation on simplified skylight model and daily energy consumption calculation.
2.4 Methodology
In this thesis project, literature review and simulation studies are two methods to evaluate skylight
system benefits.
 Literature Review
The literature review focuses on current studies of indoor visual performance of different skylight
applications through different software simulation, the energy benefit of skylight system, and the
economic benefit from energy saving of skylight system.
 Simulation Study
The daylight condition of Intelligent Workplace (IW) of Carnegie Mellon University (Pittsburgh, PA
campus) is also simulated using Radiance based on Autodesk Ecotect platform. Three different skylight
strategies, control group with no shading device, Lutron tensioned shades covered ground, and
Retrosolar Venetian blind covered ground, are simulated and compared. For venetian blinds, 4 different
blinds panel positions, fully closed, fully opened, positive 45 degree, and negative 45 degree are
simulated. The simulation is under instruction of Bertrand Lasternas and Chao Ding from School of
Architecture, Carnegie Mellon University, Pittsburgh.
The parameters used to evaluate indoor visual environment in this thesis research are, illuminance, and
daylight glare index (DGI), and unified glare rating (UGR). Illuminance (lux) is the total luminous flux
incident on a surface, per unit area. It measures how much the incident light illuminates the surface.
Daylight glare index is developed by Hopkinson at Cornell in 1972 and it’s the first metric which
considered sky as the large glare sources. Unified glare rating (UGR) is also a measure of the glare in a
given environment. The different between UGR and DGI is that it takes artificial lighting into account.
Autodesk Ecotect Analysis software is a comprehensive concept-to-detail sustainable building design
tool. In this thesis research, it is used to simulate three different skylight systems for lighting analysis in
Radiance. Radiance software is a suite of programs for the analysis and visualization of lighting in design.
Using scene geometry, materials, luminaires, time, date, and sky conditions as inputs, the software
outputs visualized images for indoor visual quality evaluation.
For light level on desk (paper-based work) and vertical screen (computer-based work), the simulation is
set under clear weather and overcast weather. Each group is simulated on spring equinox (03/21),
summer solstice (06/21), and winter solstice (12/21), respectively under these two weather conditions.

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For glare analysis, only clear weather is considered since there is no glare problem under overcast
weather. For both light level analysis and glare analysis, each group is simulated at 5 time points on each
day, 9AM, 11AM, 1PM, 3PM, and 5PM except for winter solstice day under overcast weather condition
since artificial lighting is necessary for all groups on that day. Thus, only four time points is simulated on
that day.
Due to the fact that there is inadequate information on product brochure of the glazing material and
shading device used in IW, the material simulated in Ecotect is not exactly the same. The data collected
in field test is used to calibrate the simulation.
A simplified skylight model is made in this thesis project to quantify energy benefit of dynamic skylight.
The model is made in Design Builder and then exported into Energy Plus. The energy use intensity (EUI)
is calculated by Energy Plus for each six skylight strategy. The energy consumption for two proposed
skylight schedule is then calculated.
In this project, the thesis process flow chart is shown in Figure 1.2.1. The model is built in Autodesk
Ecotect based on original IW model in Autodesk Revit. Then models are exported into RADIANCE for
parameter calculation. Based on the analysis of calculation results, the recommendation of skylight
strategies schedule is provided.
Figure 1.2.1 Simulation Software Diagram

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3. Background of U.S. Energy Consumption
According to data published by U.S. Energy Information Administration (EIA), commercial and residential
building energy make 39% of total energy consumption in U.S. in 2012 (EIA, U.S. Energy Information
Administration, 2012). If skylight systems can be applied into most of commercial and residential
buildings, there could be a huge energy saving.
Figure 1.3.1 Major Energy Usage Breakdown in U.S. 2012 (EIA, U.S. Energy Information Administration, 2012)
From the commercial sector energy consumption survey conducted by EIA (EIA, U.S. Energy Information
Administration, 2014) (Figure 1.3.2), it is shown that from 2000 to 2014, the electricity retail sales to
commercial building sector almost remains steady. However, the average retail price of electricity for
both residential and commercial sector shows an increasing tendency (Figure 1.3.3). Thus, it is a huge
opportunity for skylight applications in commercial buildings since daylight can reduce electricity
consumption in artificial lighting and heating/cooling sectors. The saved electricity energy from skylight
systems can bring economic benefits as a result.
Figure 1.3.2 Average Retail Price of Electricity (EIA, U.S.
Energy Information Administration, 2014)
Figure 1.3.3 Commercial Sector Energy Consumption (EIA,
U.S. Energy Information Administration, 2014)
Commercial
18%
Residential
21%
Transportation
28%
Industrial
33%
U.S. Energy Consumption, 2012

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From residential building energy usage breakdown in 2005 (Figure 1.3.5), it is shown that space heating
and cooling are still the major energy consumption sectors. Lighting makes 11% in total energy
consumption. And for commercial buildings (Figure 1.3.4), lighting energy consumption takes 26% of
total energy use. Space heating and cooling take 14% and 13%, respectively. Since these parts make 53%
of primary energy use, skylight system is more beneficial for commercial buildings compared with
residential buildings.
Figure 1.3.4 Commercial Primary Energy End-Use Splits, 2005 (Energy, 2008)
Figure 1.3.5 Residential Primary Energy End-Use Splits, 2005 (Energy, 2008)
Figure 1.3.6 shows the total floorspace distribution of buildings in northeast region. Office buildings take
the largest part of total building floorspace in northeast U.S. Office buildings also have the largest
energy consumption in northeast region (Figure 1.3.7). Besides, according to Rocky Mountain Institute,
73% of commercial buildings (by number) are under 10,000 square feet in size (Institute, 2014). These
three facts indicate that skylight system can bring large energy saving benefit for commercial office
buildings in northeast U.S. compared with other kinds of buildings.
Lighting
26%
Space
Heating
14%Space
Cooling
13%
Ventilation
6%
Water Heating
7%
Electronics
6%
Refrigeration
4%
Computers
3%
Cookings
2% Other
19%
Commercial Primary Energy End-Use Splits
Lighting
11%
Space
Heating
31%
Space Cooling
12%
Wet Clean
5%
Water Heating
12%
Electronics
7%
Refrigeration
7%
Computers
1%
Cookings
5%
Other
9%
Residential Primary Energy End-Use Splits

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Figure 1.3.6 Total Floorspace of Building in Northeast Region
(Pei, 2013)
Figure 1.3.7 Major Fuel Consumption in Northeast Region
(Pei, 2013)
Comparing renewable energy consumption between residential and commercial use (Figure 1.3.8),
residential renewable energy shows a much more oblivious increase than commercial use. Renewable
energy use in commercial sector does not show much fluctuation during recent 10 years. This shows a
great potential for renewable energy use in commercial building sector. Specifically, for skylight systems
design, solar panel can be integrated into design. One example is the combination of skylight and semi-
transparent photovoltaic. This kind of system can generate electricity through solar energy, which
increase energy performance of the skylight.
Figure 1.3.8 Renewable Energy Consumption: Residential and Commercial Sectors (EIA, U.S. Energy Information
Administration, 2014)

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4. Literature Reviews of Skylight Benefits
This section provides literature reviews of daylighting simulation and field test research relating with
skylight energy and economic benefits. The research includes different climate zones, mainly climate
zones similar to Pittsburgh, which is the research zone in this thesis project. Different skylight systems
are studied and summarized in this literature review as well. Suitable skylight systems for different
building types, including classrooms, gymnastics, museums, and office buildings, are studied in these
researches. Some researches include simulation using computer software, which provide guideline for
daylight analysis in this thesis.
This literature review summarizes different skylight systems for different building types, the related
benefits, and research method for doing skylight simulation. It helps finding useful information used in
this thesis project. Some of researches studied in this thesis project analyze economic benefits of
skylight systems (li, Lam & Chang, Chel, Tiwari, & Chandra), the research methods provided in these
researches largely supplements the missing economic analysis missing in previous research. The
research conducted by Tagliabue et al in 2012 provided the overall concept and process for computer
simulation on daylighting system, and daylight benefits as well. One interesting point in these
researches studied in the combination of lighting dimming control and daylighting (Athienitis &
Tzempelikos, 2012). This research provides a more energy efficient way for daylighting system design,
which could be analyzed further. Table 4.1 summarizes benefits of skylight strategies, and Table 4.2
summarizes research methodology on skylight computer simulation.
4.1 Daylight utilization in perimeter office rooms at high latitudes: Investigation by computer
simulation (Dubois & Flodberg, 2011)
In 2011, M-C Dubois, K. Flodberg from University of Lund conducted simulation study of daylight
autonomy in perimeter office rooms at high latitudes. Using RADIANCE based simulation program
DAYSIM, following variables are studies: Glazing-to-wall ratios, climate, orientation, inner surface
reflectance, glazing visual transmittance. For each simulation model, continuous daylight autonomy
(DAcon) and daylight autonomy max (DAmax) were analyzed.
Research Method
The parametric study was achieved using DAYSIM program. Office models with different GWR were
used for calculations and data analysis. And for each case, continuous daylight autonomy and daylight
autonomy max were calculated for comparison.

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Results
This paper shows that the north orientation presents good DAcon potential and no direct sunlight risk
even with large GWR. It also shows that inner wall reflectance has significant effect on GWR as
orientation. Simulations with low-transmittance glazing (Tvis = 36%) showed that larger GWR (60%) are
needed to obtain the same DAcon as ‘small’ GWR (20%) with relatively little reduction in direct sunlight
risk [1]
. It is also shown in this study that DAcon is slightly reduced with the use of a Venetian blind in the
case of an active user who manages the blinds coherently [1]
. The study of different electric lighting
dimming and switching strategies showed that the choice of electric lighting system generally has more
effect on energy use than the GWR. Part of the research results is shown in Figure 10 and table below.
Figure 4.1.1 DAcon (%, top) and DAmax (%) as a function of GWR (%) in relation to distance from glazing for single-cell,
south-oriented office in Stockholm
Glazing-to-wall ratio (GWR) DAcon DAmax
Effect of GWR for South-oriented office in Stockholm
Stockholm 10% 62% 2%
30% 78% 7%

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40% 80% 10%
60% 83% 22%
Effect of GWR relative to climate for a South-oriented office
Montreal 10% 63% 3%
30% 82% 10%
40% 90% 14%
60% 92% 23%
4.2 A model for estimation of daylight factor for skylight: An experimental validation using pyramid
shape skylight over vault roof mud-house in New Delhi, India (Chel, Tiwari, & Chandra, 2009)
In 2009, Arvind Chel et al used experimental hourly inside and outside data of an existing skylight
integrated vault roof mud-house to investigate and validate daylight factor in composite climate of New
Delhi. Three different practical horizontal surface levels ground, 75cm above ground, and 150cm above
ground) were modeled inside the big and small dome rooms.
Research Method
Illuminance level inside the room at the working surface as compared to the diffuse illuminance
available outside the building is used for determining daylight performance of building. The energy
saving potential of daylighting was evaluated based on the inside illuminance flux and efficacy of lamp to
be operated for getting same illuminance flux as that of natural daylight using roof integrated skylight.
The experimental value of daylight factor for the room was determined based on the percentage ratio of
inside illuminance on the working area to outside diffuse illuminance.
Results
The illuminance level inside mud-house in this research was found sufficient for office work inside the
room and the illuminance level was found 100 lux (minimum) inside both small dome and big dome
rooms from 10AM to 3PM in all months of the year. The experimental daylight factor over the year for
big and small dome rooms are found in the range of 1.5-3.5% and 2.5-7%, respectively, based on skylight
performance in both winter and summer. The total annual average artificial lighting energy saving
potential corresponding to the skylight illuminance in the existing building was estimated as
973kWh/year corresponds to mitigation of CO2 emissions 1526 kg/year. And the vertical distance above
floor surface for the skylight plays important role towards the amount of light output reaching on the
surface[2]
.

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The research also points that total lighting energy saving potential and annual mitigation of CO2
emission will be around 146 million kWh/year and 0.23 million metric tons per year if 5% of the total
households in Delhi state are built with mud-house like mentioned in the paper. Also, if 5% of the total
households in India are made of mud-house integrated with skylight in rural areas or semi-urban areas,
the annual lighting energy saving and annual CO2 emission mitigation will be about 6811 million
kWh/year and 10.7 million metric tons per year. Some detailed results are shown in Figure 11 - 14.
Figure 4.2.1 Hourly Energy Saving Potential of Skylight in Big Dome Building in January
Figure 4.2.2 Hourly Energy Saving Potential of Skylight in Small Dome Building in January

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Figure 4.2.3 Hourly Energy Saving Potential of Skylight in Big Dome Building in June
Figure 2 Hourly Energy Saving Potential of Skylight in Small Dome Building in June
Benefits
For skylight of small and big dome:
 Average annual energy saving: 204 kWh/year and 564.5 kWh/year
 Mitigation of CO2 emissions: 265-375 kg/year and 732-1038 kg/year
 Carbon credit potential: $2.7-$3.8 per year and $7.3-$10.4 per year
 For mud-house with skylight integrated two small and one big dome shape rooms:
 Total artificial lighting energy saving: 973 kWh/year
 Mitigation of CO2 emissions: 1526 kg/year
 Carbon credit potential: $15.3/year

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4.3 Dynamic simulation and analysis of daylighting factors for gymnasiums in mid-latitude China (Zhao
& Mei, 2013)
In 2013, Yang Zhao and Hongyuan Mei from China divided 22 different design factors on interior
daylighting effects into three categories according to its relative impact, very high impact: latitude, date,
window position, glazing transmittance, building height, building depth and window area; general high
impact: reflectance of glazing, wall, ceiling and floor, building length, light attenuation of window
structure and light attenuation factor of indoor structure; little impact: time of day, orientation
coefficient, light reduction factor of outdoor obstruction, light reduction factor of wind deflector block,
cleanliness of window, and the surface area of wall, ceiling and floor.
Research Method
Using DIALux, a computer package for simulating and visualizing lighting in and around architectural
environments using backward radiosity calculation, mathematical model is used for daylighting factors
analyzing and classifying. Gymnasiums were modeled according to relative Chinese design code. The
year is divided into 24 time periods as calculation time. And three different locations located between
30 and 60 north were chosen for simulation.
Results
The research found out following point: 1. the required window area is smallest at the summer solstice
irrespective of the type of gymnasium. 2. The window area required when using a skylight is much
smaller than that of each side window design. 3. The required window area increases with reduced
glazing transmittance. 4. Irrespective of the type of gymnasium, the required skylight area shows a linear
increase with an increase in building height. 5. Greater building depth requires larger window area,
irrespective of the window position.
Integrated daylighting simulation into the architectural design process for museums (Kim & Seo, 2012)
In 2012, South Korea researcher Chang-Sung Kim and Kyung-Wook Seo found that a lighting design
method for exhibition spaces in museums is suggested. Researchers used both scale models tests and
simulations using RADIANCE to validate this method. The corrected results of simulation were applied to
existing museum to confirm the performance of the method in modeling an actual environment. By
modulating and controlling the parameters, the appropriate dimensions of the monitor-shaped toplight
for the museum were determined.
Research Method

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Architectural characteristics of the existing museum- Seoul Museum of Art were analyzed for
determining a new daylighting system. The illumination levels for the target area were defined
according to IESNA. A scaled model was measured and compared with simulation study using
RADIANCE. And integrated daylighting simulation was conducted based on the correction of simulation
results. The Figure 15 shows the simulation model in this study.
Figure 4.3.1 Picture of MT Model Simulations
Results

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The existing pyramid-shaped skylight provides a 54260lux illuminance level for direct sunlight into the
space on the summer solstice and 43720lux on the autumnal equinox, which is damaging in summer.
The relative errors between scaled model and Radiance simulation in this study were 35% to 45% on
average, however, the corrected simulations greatly reduced the differences to the range of 3% to 9%.
The study also proposed monitor-shaped toplight (MT) design models for the museum – 60MT23,
70MT23, 80MT23, 90MT23, 80MT14, and 90MT14. (The two digits after MT indicate the window height
and light well depth, and the number before MT indicates transmittance value.)
4.4 Energy saving through the sun: Analysis of visual comfort and energy consumption in office space
(Tagliabue, Buzzetti, & Arosio, 2012)
In 2012, Lavinia Chiara Tagliabue et al from Milan, Italy conducted a study to simulate energy saving
impact of daylighting system in office buildings. Optimization of daylighting, electrical consumption and
visual comfort are studied. A single office space with three different configuration of the openings
located in different orientation and position (south exposed window, north exposed window and
skylight) were simulated as three cases. Six simulation softwares, Autodesk Ecotect, Radiance, Evalglare,
Daysim, Dialux, and Energy Plus were used in this study.
Research Method
In this research, Ecotect was used to model three different daylight settings. Radiance, Evalglare, and
Daysim were used to calculate visual comfort parameters (luminance, illuminance, daylight factor,
daylight glare probability, daylight glare index, unified glare rating, daylight autonomy, and useful
daylight index). Energy Plus did calculation of heating and cooling demands. And Dialux calculated
electrical consumption for lighting. The office space was set to be a single unit which can be occupied by
two or three people located in Milan, northern Italy.
Results
The detailed calculation result is shown below.
Case NW Case SW Case SL
Energy Simulation (kWh/m3/year)
Heating Consumption 5.49 3.31 6.04
Cooling consumption 6.64 12 5.93
Electric equipment 21.9 21.9 19.71
Illumination without control 20.97 20.97 27
Illumination with control 11.52 11.52 27
Lighting simulation
Daylight Factor (%) 11.31 11.31 4.18
UDI (%): <100, 100-20000, >2000 8, 14, 78 8, 11, 81 17, 50, 33
DA (%) 73-93 76-93 42-67
The study shows that skylight system can provide a more homogeneous daylighting distribution for
indoor space, although the level of illuminance level cannot reach the comfort levels for visual tasks. If

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considering the whole energy consumption, north window would be optimal daylighting system. And it
can ensure visual comfort parameters without strong negative effects on energy consumption.
Benefit
A reduction of almost 30% on thermal consumption compared with south window case and 1% with
north window case.
4.5 Towards an analysis of the performance of lightwell skylights under overcast sky conditions
(Acosta, Navarro, & Sendra, 2013)
In 2013, Ignacio Acosta et al from Spain studied one of skylight systems-lightwell skylight (Figure 16)
under overcast sky condition. Daylight factors and luminous distribution produced inside a room were
studied. Several parameters of were analyzed: size and height/width ratio of the skylight, reflection
index of lightwell, different room proportions, and suitable spacing between skylights.
Research Methods
The simulation software used in this study is Lightscape 3.2. The initial simulated room was a
9m9m4.5m room and with a lightwell skylight placed in the center of the roof. The work plane on
which daylight factors are studied was located 1m above the floor. 4 trials regarding skylight size and
ration, reflection index of the skylight, room size and skylight spacing were simulated respectively.
Results
Trial 1- size and ratio of the lightwell skylight shows that the illuminance generated by it is almost
directly proportional its size. Trial 2- reflection index of the lightwell skylight proves that it is a
determining factor for illuminance. It is also deduced from this trial that in cases where the reflection
index of the skylight is between 0.5 and 0.7, considering a height/width ratio of the lightwell greater
than 2, the daylight factors are almost proportional to the reflection index. Trail 3- room ratio shows
that different room heights have little impact on daylight factors. And trial 4-lightwell spacing shows
that the uniformity of illuminance is proportional to the width/height ratio of the lightwell in the
absence of a reflected component.
Figure 4.5.1 Lightwell Skylight

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Benefits
The skylight with a reflection index of 0.7 produces an increase in illuminance of over 30% compared to
the skylight with an index of 0.5 which produces a similar increase compared to skylight with an index of
0.3.
4.6 Energy and cost studies of semi-transparent photovoltaic skylight (Li, Lam, & Cheung, 2009)
In 2009, Danny H. W. Li et al from City University of Hong Kong analyzed the thermal and visual
properties, energy performance, and environmental and financial issues of semi-transparent
photovoltaic skylight. Researchers measured solar irradiance and daylight illuminance of the skylight.
The electricity generated by the skylight was also measured. The thermal and visual performance of PV
skylight with lighting control was evaluated as well.
Research Method
Data was collected from a transparent glazing and multi-crystalline silicon solar cells installed in a
primary school in Hong Kong. Researchers used pyranometers, illuminance meters and power analyzer
to measure solar irradiance, daylight illuminance and electricity generated by the skylight for both
summer and winter conditions. Case studies on a circulating atrium were also conducted to evaluate the
energy use, cooling requirements and monetary implications when the PV skylights together with the
daylight-linked lighting controls were applied. Four case were analyzed, tinted glass for the skylight
without dimming controls (base case); tinted glass for the skylight with dimming controls (case 2);
installing the semi-transparent solar modules to replace tinted glass for the skylight without dimming
controls (case 3); and installing the semi-transparent solar modules to replace tinted glass for the
skylight and with dimming controls (case 4).
Results
Field measurements of the skylight shows that transmittances for diffuse daylight and irrandiance can
be described by constant values of 20.1% and 21.5%, respectively. When direct beam components were
included, both the visible transmittance and solar transmittance could be described by 3rd
order
polynomial functions. The daily mean energy conversion efficiency was found to be 10.83%. The Figure
17 and 18 show electricity benefits and peak load reduction between case 2 and 4.
Benefits
The major benefits in this study are shown in Table 1.
Table 4.6.1 Case Benefit
Cases 2 3 4
Emissions reductions (kg)
CO2 12400 27950 40300
SO2 38 86 123.8
NOX 21 47 68.3
Particulates 2 4 5.3
Monetary payback years

21
Payback (considering electric
tariff only) 1.1 38.6 27
Payback (considering electric
tariff, chiller plant, cost and
CO2 trading)
0.8 32.8 23
Figure 4.6.1 The Electricity Benefits (Electricity Generated Plus Electricity Saved) for Case 2-4
Figure 4.6.2 The Peak Load Reduction for Case 2-4
4.7 A methodology for simulation of daylight room illuminance distribution and light dimming for a
room with a controlled shading device (Athienitis & Tzempelikos, 2002)
In 2002, A. K. Athienitis and A. Tzempelikos from Concordia University, Canada simulated an office room
with an advanced window system and calculated minimized electric due to the installation of dimming
controls. The particular system considered in this study is a double-glazed window with motorized highly
reflective blinds between the two glazings installed in an outdoor test-room and operated by a custom-
built computerized building automation system. []
The incidence angle, shading device position, and sky
conditions were analyzed. Both clear sky and overcast sky conditions were simulated. Daylight

22
illuminance on the work plane is analyzed in this study. And the result of field experiment and
simulation was compared.
Research Methods
The study determines the optimal shading device angle to get maximum daylight without causing glare
issues. A field experiment was conducted outdoor in Montreal. Test-room is 2.32.72.4 m with double-
glazed low-e coating and highly reflective louvers integrated between the two panes window. Using
solar radiation and daylight sensors, solar radiation and its visible portion were measured. For
simulation part, illuminance due to daylight at several points on the work plane for representative days
in each month, once every hour, from 9 AM to 5 PM was calculated. Researchers computed the energy
savings from the blinds and dimming control. The 553m simulated office locates in Montreal. Based
on the simulation, suggestions have been made.
Results
The comparison between field experiment and simulation is shown in figure 19.
Figure 4.7.1 Comparison of Measured and Predicted Illuminance Level due to Daylight
Benefits
The energy saving for the particular window in this study system with integrated blinds can exceed 75%
for overcast days and 90% for clear days, comparing with the case of no daylighting/dimming control.

23
The Table 4.1 summarizes case studies of benefits of different types of skylight strategies. Table 4.2
summarizes simulation studies. Some of these studies in Table 4.2 are in climate zones different from
Pittsburgh, some of them simulated other building types other than office building, and some of them
study other daylight applications other than skylight. However, all these studies provide detailed
information on how to use different software to conduct computer simulation. Thus, all these studies
are important guideline for this thesis project.
4.8 Lockheed 157 (Thayer, 1995)
The office building built in 1983 in Sunnyvale, California is a 5-story building with daylight applications.
The west and east façade of the building minimized the glazing area. An atrium with 18,000 sf area
locates between office spaces from the ground floor to the roof. On each floor, there are two separate
office area facing south and north. The daylight is provided through glazing on north and south façade
and through skylight of the atrium. There are also light shelves installed on both exterior and interior
facades assisting daylight to reach deeper into office area.
Skylight Type
4 rows of sawtooth shaped skylight with vertical north-facing clear glass and sloped south-facing
diffusing glass.
Benefits
 Reduced 15% of absenteeism compared with originally 7%.
 The energy saving per year leads to a $500,000 reduction on energy bill.
4.9 Simulation study on Los Angeles, Atlanta, and New York (Fontoynot M., 1984)
A simulation study was conducted based on a single-story office building in Los Angeles, Atlanta, and
New York respectively. The energy performance of the simulation model in each city is compared under
condition with and without daylighting application using the BLAST program. Daylighting dimming
control and roof monitors are simulated as daylight strategies in this study. Two lighting power density
are tested in this study, 2.5W/sf and 1.5 W/sf.
Skylight Type
Roof monitors with dimmable light control system.
Benefits
 In 1.5 W/sf lighting power density model, the reduction on annual lighting energy is 48%.
 In 2.5 W/sf lighting power density model, the reduction on annual lighting energy is 49% and on
cooling energy is 13%.
4.10 Simulation study on prototypical federal government building (U.S. DOW & FEMP, 2002)

24
Based on the federal building in Baltimore, Maryland, a simulation study is conducted. The building has
a floor area of 20,000 sf and it is a two-story building. This simulation focuses on equipment
improvement. The software used in this study to calculate energy consumption and cost is DOE.2e.
Skylight Type
General skylight with dimmable light control system
Benefits
The electricity consumption reduction is 3.8%.
4.11 California State Automobile Association (Daylighting Initiative, Pacific Gas and Electric Company,
1997)
The office building of California State Automobile Association in Antioch, California was studied in a
research conducted by Daylighting Initiative. The building has a floor area of 15,000 sf. Daylight is
gained through perimeter windows and skylights in this building. The skylight wells locate 5 feet higher
than the perimeter ceiling and are located every 20 feet in the office. The skylight is also operable for
natural ventilation. The building also has dimmable lighting system to reduce light power output from
100% to 20% and light input from 100% to 40%. Of all the interior lighting, 68% of them are under
dimmable control system.
Skylight Type
Triple-pane, acrylic, low-glare operable skylight wells, light sensors installed on louvers, dimmable
lighting control system, and fixed-pitch perforated window blinds
Benefits
A reduction of 32% of electrical lighting energy consumption
4.12 ACE Hardware store (Daylighting Initiative, Pacific Gas and Electric Company, 1999)
Daylighting Initiative conducted a study on the ACE Hardware store in El Cerrito. The building has a floor
area of 14,400 sf. The skylight in this building is produced by So-luminaire Daylighting System
Corporation and is integrated with movable mirror and infrared sensor. The sun can be tracked from
sunrise to sunset by the system.
Skylight Type
Active skylight integrated with movable mirror and infrared sensor, sun-tracking system
Benefits
A reduction of 65% on annual lighting energy consumption

25
4.13 A-1 Cold Storage Warehouse (Ciralight)
A-1 cold storage warehouse is built in 2003 with a floor area of 12,000 sf in Inglewood, California. There
is no window on exterior 8-inch thick concreate wall. The building is used as office area and warehouse.
The renovation project is done by Ciralight. The renovation includes adding daylighting with illumination
equivalent to 19,200 watts of fluorescent lights. The cost of vertical fenestration is saved since the
building’s skylight strategy focuses on ceiling skylight.
Skylight Type
The three mirror skylight system is integrated with GPS device which will track the path of the sun and
harvest the maximum sunlight to illuminate indoor spaces. The skylight system has a U-value of 0.35 and
SHGC 0.3196.
Benefits
Monthly saving on utility bills is $1000. The total electricity energy consumption reduction is equivalent
to 1.2 million ft3
of CO2 emission annually.
4.14 PetSmart Stores (Southern California Edison, 2008)
Skylights and energy management system were installed into PetSmart store in Modesto, California, in
2008. The dimmable control system connects to 52 of 77 fluorescent lighting fixtures. The illuminance
level is measured by hand held light meter from August 22nd
to September 10th
in 2008. The standards
used for evaluation is IESNA for open plan office. The result shows only 2 out of 9 measurements in the
electric light off case is lower than the recommendation.
Table 4.1 Skylight Strategy Benefit
Location HDD CDD
Floor
area (sf)
Story Skylight Type
Dimmable
System
Energy Saving
Total Heating Cooling Lighting
Sunnyvale, CA 2210 475 585000 5
Static Sawtooth
skylights
Yes 50%
New York, NY 4669 1272 10000 1
Static Roof
Monitors
Yes 10% -4% 9% 43%
Atlanta, GA 2689 1763 10000 1
Static Roof
Monitors
Yes 15% 14% 49%
Los Angeles,
CA
893 1218 10000 1 Static Skylight Yes 18% 17% 55%
Baltimore,
MD
3536 2026 20000 2 Static Skylight Yes 4%
Antioch, CA 2543 826 15000 1
Skylights with
louver shadings
Yes 9% 32%
El Cerrito, CA 2376 193 14400 1
Skylight with sun
trackers
Yes 28% 65%
Inglewood,
CA
1066 717 12000 1
Skylight with sun
trackers
Yes 52% 58%
Modesto, CA 2311 1673 23500 1 Static Skylight Yes 9% 20%

26
Table 4.2 Simulation Literature Review Matrix
Case Name Year
Building
Type
Location
Daylight
Strategy
Study Object
Benefits Simulation
ProgramQuantitative Qualitative
Daylight utilization
in perimeter office
rooms at high
latitudes: computer
simulation (Dubois
& Flodberg, 2011)
2011
Office
Building
Multiple
locations
(Stockholm,
Ostersund,
Malmo,
Gothenburg,
Montreal,
Quebec)
Single
window
located on
the 2.4m
wide facade
Glazing-to-wall ratios,
climate, orientation, inner
surface reflectance, glazing
visual transmittance,
venetian blind management,
electric lighting dimming and
switching systems
 For high altitude area office rooms: an optimal glazing-to-wall (GWR)
ratio ranging between 20% and 40%, with a north orientation requiring a
larger GWR (40%), a south orientation a smaller GWR (30%).
 The reflectance of inner surfaces has a significant effect on daylight
autonomy and the use of low transmittance glazing demand a large
GWR (60%) to achieve the same daylight autonomy as 20% GWR with
high transmittance glazing.
Radiance,
Daysim
Simulation and
experimental
validation using
pyramid shape
skylight over vault
roof mud-house in
New Delhi (Chel,
Tiwari, & Chandra,
2009)
2009 Classroom New Delhi
Skylight
integrated
vault roof
mud-house
Illuminous flux, lighting
power, daylight factor,
mitigation of CO2 emission
related to skylight
 For skylight of small and big dome:
o Average annual energy saving: 204 kWh/year and 564.5
kWh/year
o Mitigation of CO2 emissions: 265-375 kg/year and 732-1038
kg/year
o Carbon credit potential: $2.7-$3.8 per year and $7.3-$10.4 per
year
 For mud-house with skylight integrated two small and one big dome
shape rooms:
o Total artificial lighting energy saving: 973 kWh/year
o Mitigation of CO2 emissions: 1526 kg/year
o Carbon credit potential: $15.3/year
NA
Dynamic simulation
and analysis of
daylighting factors
for gymnasiums in
mid-latitude China
(Zhao & Mei, 2013)
2013 Stadium Harbin
Windows on
side wall
and skylight
Correlation between 22
daylight design parameters
and interior daylighting
effects
 The required window area is smallest at the summer solstice irrespective
of the type of gymnasium.
 The window area required when using a skylight is much smaller than
that of each side window design.
 The required window area increases with reduced glazing transmittance.
 Irrespective of the type of gymnasium, the required skylight area shows
a linear increase with an increase in building height.
 Greater building depth requires larger window area, irrespective of the
window position.
DIAlux
Dalighting Design
for Museums (Kim
& Seo, 2012)
2012 Museum Seoul
Monitor-
shaped
toplight
Visual impact of skylight in
real building comparison
 Daylighting simulation method can
become an integral part of the
architectural design that can produce a
 60MT23, 70MT23,
80MT23, 90MT23,
80MT14, and 90MT14
Radiance

27
skylight predictable lighting environment for a
museum.
are proposed as
alternative designs for
the museum.
Lightwell skylights
under overcast sky
conditions (Acosta,
Navarro, & Sendra,
2013)
2013
Office
Building
Seville
Lightwell
skylight
Daylighting factors according
to skylight ration and
illuminance depending on
the reflection index of the
skylight
 Reflection index is a determining factor
for illuminance.
 Daylight factors are proportional to the
reflection index (skylight height/width
ratio > 2).
 Room heights have little impact on
daylight factors.
 Uniformity of illuminance is proportional
to the width/height ratio of the skylight.
 From reflection index
0.5 to 0.7, illuminance
is increased by 30%.
 From reflection index
0.3 to 0.5, illuminance
is increased by 30%.
Lightscape
Energy and cost
studies of semi-
transparent
photovoltaic
skylight (Li, Lam, &
Cheung, 2009)
2009
Office
Building
Hong Kong
Semi-
transparent
photovoltaic
skylight
Thermal and visual
properties, energy
performance, environmental
and financial issues of
skylight
 The semi-transparent PV skylight with dimming control has an annual
electricity saving of 56.9 MW and peak cooling load reduction of
29.3kW.
 The skylight system has an annual emissions of CO2, SO2, NOx and
particulates reduction of 40300, 124, 8.5, and 5.3 kg respectively.
 The simple monetary payback is 23 years.
LabVIEW
Skylight and light
dimming for a
room with a
controlled shading
device (Athienitis &
Tzempelikos, 2002)
2002
Office
Building
Montreal
Window
with
dimming
control
Combined daylighting-
lighting system numerical
simulation and visual
performance evaluation
 Daylight transmittance is a function of
sky condition, blind tilt angle and angle of
incidence.
 The energy savings
using light dimming
control window
system with integrated
blinds can exceed 75%
for overcast days and
90% for clear days.
NA
Energy saving
through the sun:
Analysis of visual
comfort and
energy
consumption in
office space
(Tagliabue,
Buzzetti, & Arosio,
2012)
2012
Office
Building
Milan
Daylight on
north side
wall, south
side wall,
and skylight
Daylight energy
conservation and visual
comfort
 Skylight system can provide a more
homogeneous daylighting distribution for
indoor space
 If considering the whole energy
consumption, north window would be
optimal daylighting system.
 Skylight can ensure visual comfort
parameters without strong negative
effects on energy consumption.
 A reduction of almost
30% on thermal
consumption
compared with south
window case and 1%
with north window
case.
Ecotect,
Radiance,
Evalglare,
Daysim,
Energy Plus,
Dialux

28
5. Introduction of Daylighting Simulation Software
Table 5.1 Introduction of Daylighting Simulation Software
Tool Input Output Strengths Keywords
Latest
Version
Energy
Plus
Energy Plus uses a
simple ASCII input file.
Private interface
developers are already
developing more
targeted / domain
specific user-friendly
interfaces.
Energy Plus has a
number of ASCII output
files - readily adapted
into spreadsheet form
for further analysis
including building
annual heating and
cooling consumption.
Accurate, detailed
simulation capabilities
through complex
modeling capabilities.
Input is geared to the
'object' model way of
thinking. Successful
interfacing using IFC
standard architectural
model available for
obtaining geometry from
CAD programs. Extensive
testing (comparing to
available test suites) is
completed for each
version and results are
available on the web
site. Weather data for
more than 1250
locations worldwide
available on the web
site.
Energy
simulation,
load
calculation,
building
performance,
simulation,
energy
performance,
heat balance,
mass balance
V8.2 (2014)
Adeline
Geometry and surface
characteristic codes
input using 3-D CAD
(SCRIBE Modeler);
simple geometry can
also be entered via
dialog boxes; analysis
runtime parameters
(e.g., geographic
location, time of year,
sky conditions) entered
via graphic user
interface dialog boxes.
Various graphic displays
of interior illuminance
levels, including 3-D
renderings; also
preformatted text files
containing detailed
analysis results that can
be passed on to dynamic
building simulation
programs such as tsbi5,
SUNCODE, DOE-2 and
TRNSYS.
3-D CAD input; complex
geometry allowed;
accurate daylighting and
electric lighting
calculations; graphic
display of analysis
results.
Daylighting,
lighting,
commercial
buildings
V3.0 (2002)

29
Evalglare
Image to be evaluated
(smaller than 800800
pixels)
Daylight glare
probability (DGP) and
image given in the
RADIANCE image format
(.pic or .hdr)
The program calculates
the daylight glare
probability (DGP) as well
as other glare indexes
(dgi,ugr,vcp,cgi) to the
standard output.
180° fish-eye-
image, glare
source
evaluation
and
simulation
Ecotect
From simplest sketch
design to highly
complex 3D models,
3DS and DXF files
Specific
analysis/validation:
RADIANCE, POV Ray,
VRML, AutoCAD DXF,
EnergyPlus, AIOLOS,
HTB2, CheNATH, ESP-r,
ASCII Mod files, and XML
Essential analysis
feedback provided,
daylight factors and
illuminance levels
calculated at any point in
the model, sun’s
position and path
displayed relative to the
model at any date, time,
and location
Environmenta
l design and
analysis, solar
control,
overshadowin
g, natural and
artificial
lighting, life
cycle
assessment
and costing
Ecotect
2012 (2012)
Daysim
RADIANCE building
scene files, a RADIANCE
sensor point grid file,
EnergyPlus weather
data
Annual
illuminance/luminance
profile, daylight
autonomy/factor
distribution, annual
electric lighting energy
use
Field study data based
user behavior model,
energy saving potential
estimation
Annual
daylight
simulations,
electric
lighting
energy use,
lighting
controls
Daysim 4.0
（2013）
Radiance
Geometry and
materials of design
space, DXF, Architrion,
and IESNA standard
luminaire files,
ArchiCAD, Vision3D
Luminance and
illuminance values, plots
and contours, visual
comfort levels,
photograph-quality
images and video
animations
Physical accuracy in a
graphics rendering
package, reliability and
source code availability,
arbitrary surface
geometry and
reflectance properties
Lighting,
daylighting,
rendering
Radiance
4.2
（2014）
DIALux
Self-created file, DWG
or DXF file,
photometric files like
IES, EULUMDAT, CIBSE
TM14, or LTLI
Pictures (JPG, BMP),
movies (AVI), electronic
printouts (DXF, DWG,
PDF)
Useful for for doing both
the architectural and the
technical lighting design
Lighting
design,
daylight and
artificial
lighting,
emergency
lighting, road
lighting
DIALux evo
3.3

30
AGI32
Project dimensions,
luminaire photometry
(light fitting data) in IES
standard format,
surface color and
reflectance, texture, 3D
models
Numeric results of
Illuminance, luminance,
exitance, BMP or VRML
file, luminance or
illuminance patterns on
all surfaces image,
radiosity based
rendered ouputor
radiosity
Numerical analysis and
fast high quality
rendering for exterior
and interior lighting and
daylighting
Lighting,
daylighting,
rendering,
roadway
AGI v15
(2014)
In this research, Ecotect will be used for Intelligent Workplace modeling since it can be used as platform
simulation software for Radiance lighting analysis. Radiance will be used for both light level and glare
analysis. The reason for choosing this software is that: Radiance has no limitation on geometry or the
materials that may be simulated and all the metrics used in this thesis project can be calculated by it.
Besides, simulation model can be exported into Radiance easily.
6. Dynamic Skylight Strategy Simulation and Energy Analysis
6.1 Pittsburgh Climate
For skylight system design, climate should be considered as an important factor in order to reach best
visual and energy performance of skylight. For example, the selection of glazing material can affect
insulation of the building, which can result in change of energy consumption. The weather condition
affects visual performance of skylight system. The skylight works better in clear day than cloudy and
rainy days. It also has effect on building’s solar energy gain from skylight. This section provides a basic
climate introduction of Pittsburgh.
Pittsburgh’s location is in the humid continental climate zone (Koppen Dfa/Cfa), and according to
ASHRAE, it belongs to climate 5A. Pittsburgh weather can vary dramatically from day to day; one day it
can be snowing and the next day can be hot and sunny. Seasons can be divided into 4 distinct seasons,
which are hot and humid summer, mild fall and spring, cold, cloudy, and moderately snowy winter.
From Figure 6.1.1 and 6.1.2, it is shown that the warmest month of the year in Pittsburgh is July, with an
average temperature of 72.6°F, and the coldest month of the year is January. Pittsburgh has a heating
dominated climate, which means the selection of building construction materials should put insulation
property as priority. Specifically, for skylight, the selection of glazing material should consider larger
thermal resistance. Besides, the use of skylight can help gain more solar energy, so that the heating
energy can be reduced.

31
Figure 6.1.1 Average Temperature in Each Month in Pittsburgh, Pennsylvania (WeatherSpark, 2014)
Pittsburgh temperature typically varies from 20°F to 83°F and is rarely below 5°F or higher than 90°F. In
warm season, average daily temperature is higher above 73°F, while it is only around 44°F in cold
season.
Figure 6.1.2 Average High Temperature, Average Low Temperature, and Precipitation of Pittsburgh from 1981 to 2010 (Data,
2014)

32
Skylight systems work most efficient during clear weathers. For rainy days, daylight provided by skylight
can be supplementary lighting for artificial lighting. The average total amount of annual rainfall of
Pittsburgh is 38.2 inch, with around average of 3 inch per month, and the total precipitation is greatest
in May while least in October. December and January have the most precipitation days during the year
on average, with an average 41.4 inch snowfall per season.
Figure 6.1.3 Average Humidity in Pittsburgh Each Month (WeatherSpark, 2014)
Figure 6.1.4 Average Dew Point in Pittsburgh Each Month (WeatherSpark, 2014)
According to Figure 6.1.3 and 6.1.4, the relative humidity typically ranges from 39% (comfortable)
to 92% (high humidity). The dew point typically varies from 12°F (dry) to 66°F (muggy) and is rarely
below -4°F (dry) or above 72°F (very muggy).

33
Figure 6.1.5 Monthly History – 2014 Degree Days of Pittsburgh (WeatherSpark, 2014)
Wind speed and wind direction (Figure 6.1.6 and 6.1.7) are necessary information needed for building
design. It is used for calculation of air ventilation in the building. During summer, wind flow help reduce
cooling load required for building and reduce air pollution in the building, while in winter wind flow
make the building require more energy for space heating.
Figure 6.1.6 The Average Daily Minimum (red), Maximum (black) Wind Speed with Percentile Bands (Inner Band from 25
th
to
75
th
Percentile, Outer Band from 10
th
to 9
0th
Percentile) (WeatherSpark, 2014)

34
Figure 6.1.7 Wind Directions over the Entire Year (WeatherSpark, 2014)
The direction and strength of sunlight (Figure 6.1.8) and clouds (Figure 6.1.8) are directly related to
building design. It is also very important for skylight design. It affects amount of energy required for
space heating and amount of lighting required in the building. Putting windows of façade in the
appropriate location and direction will reduce building energy consumption.
Figure 6.1.8 Sun Path Diagram of Pittsburgh (2014) (WeatherSpark, 2014)

35
Figure 6.1.9 The Median Daily Cloud Cover (Black Line) with Percentile Bands (Inner Band from 40
th
to 60
th
Percentile, Outer
Band from 25
th
to 75
th
Percentile) (WeatherSpark, 2014)
From the statistic above, there is an average of 59 clear days and 103 partly cloudy days per year, and
the median cloud cover ranges from 65% to 99%. The sky is cloudiest on January 2 and clearest
on August 12. The clearer part of the year begins around May 10. The cloudier part of the year begins
around October 29. The annual percent-average possible sunshine received value is 45% in Pittsburgh.
6.2 Autodesk Ecotect Model of Intelligent Workplace (IW)
The Robert L. Preger Intelligent Workplace is located inside Margaret Morrison Carnegie Hall, Pittsburgh,
Pennsylvania, and was completed in 1997. It is on the top of the building as an addition rooftop
construction. It integrates envelope, lighting, and mechanical systems to reach the optimal thermal,
visual, acoustic, and spatial comfort. This lab hosts faculty and graduate student offices, classrooms,
conference room, and research laboratories. In this research, the lighting analysis of dynamic skylight is
conducted in the middle part of IW. The Ecotect model is built based on Autodesk Revit model (Figure
6.2.1 and 6.2.2). The dynamic skylight field experiment area has been marked within blue area below
(Figure 6.2.3).

36
Figure 6.2.1 Plan View of IW
Figure 6.2.2 3D View of IW
In order to simulate the field experiment as accurate as possible, the windows on the side walls are
modeled in Ecotect. Modeled area is colored in purple. Figure 6.2.4 and 6.2.5 show the different
perspective of Ecotect model.

37
Figure 6.2.3 Simulated Area of IW in Ecotect
Figure 6.2.4 Perspective 1 of Simulation Area Figure 6.2.5 Perspective 2 of Simulation Area
The experiment area in IW sets up three different skylight strategies, skylight without shading device,
skylight with Retro Solar venetian blinds, and skylight with Lutron tensioned shades. This setting
increases the uncertainty of the experiment result since each experiment bay can affect each other.
Besides, windows on side walls can also affect the result of the experiment. Thus, in computer
simulation, each simulation model has the same shading device put on each skylight bay, and side
window has the same shading device with the skylight. For example, control group has no shading
device on its 5 skylight bays and side windows. Tensioned shades group has shades installed on both its
all 5 skylight bays and side windows. In order to simulate dynamic skylight strategies, four different
blinds panel positions are simulated (Figure 6.2.6). Since the simulation is aiming at an office area. Three
desks are put in the center of the indoor area to make a simulation closer to real office environment.
Since the real experiment area in IW has a complex layout including partition walls, stairways, and desks
which is difficult to build in Ecotect model, the model in Ecotect simplified all these features and it is not
an exact representation of the IW furniture layout. The rendering effect in Ecotect of four different
blinds panel is shown in Figure 6.2.7 – 6.2.22.

38
Figure 6.2.6 Blinds Panel Position
Figure 6.2.7 Blinds Panel Position - Closed Figure 6.2.8 Blinds Panel Position - Opened
Figure 6.2.9 Blinds Panel Position - Positive 45 Figure 6.2.10 Blinds Panel Position - Negative 45

39
Figure 6.2.11 Control Group Figure 6.2.12 Inside View of Control Group
Figure 6.2.13 Shades Group Figure 6.2.14 Inside View of Shades Group
Figure 6.2.15 Blinds Group (Closed) Figure 6.2.16 Inside View of Blinds Group (Closed)

40
Figure 6.2.17 Blinds Group (positive 45) Figure 6.2.18 Inside View of Blinds Group (Positive 45)
Figure 6.2.19 Blinds Group (Negative 45) Figure 6.2.20 Inside View of Blinds Group (Negative 45)
Figure 6.2.21 Blinds Group (Open) Figure 6.2.22 Inside View of Blinds Group (Open)

41
In Ecotect, two different camera perspectives are set for lighting analysis, a horizontal perspective
(Figure 6.2.25) at a height of 78.7 inch is set to simulate the visual performance of monitor surface at
sitting level, and a vertical perspective from the roof center pointing at the center of table (Figure
6.2.24) to simulate the visual performance at desk surface. The level selection is based on field
experiment conducted by Hau-Wen Wu in 2013 in IW. These two camera perspectives in Ecotect are
shown in the picture below (Figure 6.2.23). The indoor environment visual parameters are analyzed
through these two perspectives.
Figure 6.2.23 Camera Perspectives in Ecotect
Figure 6.2.24 Vertical Perspective Figure 6.2.25 Horizontal Perspective
6.3 Dynamic Skylight Shading Device
One of the main purposes in this research is to compare influence of different shading devices on the
indoor environment. In this research, two shading devices, roller shades and venetian blinds are
compared with a skylight with no shading. Four different blinds positions are also compared. The
simulation model is based on field test conducted in 2013 by Hau-Wen Wu from Carnegie Mellon

42
University. The simulated shading device in this project comes from Retrosolar and Lutron (Figure 6.3.2
and 6.3.3).
The Retrosolar venetian blinds can reflect the unwanted high-angled sunlight in summer, and redirect
the low-angle sunlight in winter into the space for daylighting and solar heat gain. The Lutron tensioned
shades is a roller shade is a roller shade specifically designed for skylights and tilted windows. (Wu, 2014)
Figure 6.3.1 Control Figure 6.3.2 Venetian Blinds Figure 6.3.3 Roller Shades
The shading device simulation in Ecotect is a similar simulation. The key parameter is simulated
according to information product brochure. The value showed in Table 6.3.1 is the combined effect of
the skylight glazing and the blinds. Since some other parameters in Ecotect are not provided by the
manufacture, the default value in Ecotect is used and then calibrated by previous data collected in field
test.
Table 6.3.1 Shading Device Specs
Product Name SHGC (Glass 0.52) SHGC (Glass 0.32) VT
RETROSolar RETROLux O
Venetian Blinds
0.13 0.1 73%
Product Name SHGC (Single Glazed) SHGC (Double Glazed) VT
Lutron Tensioned Shades 0.27 0.32 4%
6.4 Skylight Material Hypothesis
Since the specific skylight glass product is missing, a hypothesis is necessary. Six kinds of glass products
from PPG industries are selected and compared. Since the simulation location is Pittsburgh (heating
dominated), the principle for selection is to consider the insulation property of the glass. Besides, the
SHGC is very important since the main purpose for skylight is to provide daylight.
In this thesis project, following skylight material parameters are considered as important (Collaborative,
2014):
 U-Value: coefficient of measuring thermal resistance of material

43
 Solar Heat Gain Coefficient: measure of the solar energy transmittance of a window
 Light to Solar Gain: measure of material’s glazing ability to provide light without excess solar
heat gain
 Visual Transmittance: the amount of light in the visible portion of the spectrum that passes
through a glazing material.
Table 6.4.1 Comparison of PPG glass product
U-Value
Solar Heat Gain
Coefficient
Light to
Solar Gain
Visual
Transmittance
Winter
Night Time
Summer
Day Time
Solarban 60
Coating on
Starphire Ultra-
Clear Glass
0.29 0.27 0.41 1.8 74%
Solarban 60 0.29 0.27 0.39 1.79 70%
Sungate 400 0.32 0.31 0.6 1.27 76%
Sungate 500 0.35 0.35 0.62 1.19 74%
Sungate 600 0.23 0.21 0.36 1.77 63%
Starphire Ultra-
Clear Glass
1.02 0.93 0.9 1.01 91%
Based on the product sheet provided by PPG Industries, the simulation glazing material in this thesis
project is Solarban 60 (Table 6.4.1). Although Solarban 60 coating on Starphire Ultra-Clear Glass has the
best visual and thermal performance, however, due to its high price, it is not practical to use for most of
office buildings. Generally, Solarban 60 provides good insulation with relatively clearance. Thus,
Solarban 60 is chosen to be simulated in this thesis project.
For light level analysis, totally 6 × 3 × 2 × 5 = 180 simulations were made. For glare analysis, since
simulations were only made under clear weather. Thus, totally 6 × 3 × 5 = 90 simulations were made.
6.5 Simulation Process
After finishing experiment model set up in Ecotect, next step is to export the model data into RADIANCE.
The following steps show how to simulate the visual performance of control group under
1. Select the ‘RADIANCE / DAYSIM’ under ‘Export Manage’ menu and then click ‘Export Model
Data’.
2. Select ‘Illuminance Image (Lux)’ since in this case the simulation goal is to model the interior
light level of control group. (Figure 6.5.2)

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Figure 6.5.1 Light Level Simulation Step 1
3. Select ‘Final Render’ and check ‘Display image on completion’. (Figure 6.5.3)
4. Select ‘Cloudy Sky (summer)’. In this simulation project, two weather condition, ‘Sunny Sky’ and
‘Cloudy Sky’, are used in three different seasons. (Figure 6.5.4)

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5. Select ‘At Specified Date and Time’ and set the time to ‘December 21th at 3PM ‘. Five time
points, 9AM, 11AM, 1PM, 3PM, and 5PM, in are used spring equinox, summer solstice, and
winter solstice in this simulation project. (Figure 6.5.5)
Figure 6.5.5 Light Level Simulation Step
6. Select ‘Interior View’ and then hit ‘Next’ two times. (Figure 6.5.6)

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7. Select the folder saving all the files under ‘Output Options’ and click OK to begin render. (Figure
6.5.7)

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6.5 Lighting Analysis of Dynamic Skylight System
6.5.1 Standards and Regulations
From Illuminating Engineering Society of North America (IESNA), the Table 6.5.1.1 and 6.5.1.4 show the
current luminance recommendations (lux) for lighting levels in different building types. (Richman, 2014)
This standard provides comparison baseline for the simulation. And Table 6.5.1.2 provides the
illumination requirement of different activities (Richman, 2014). The values in table 5 are maintained
average illuminance value and values in table 6 is the minimum value of illuminance for different
activities.
Table 6.5.1.1 Office Building Lighting Standard (Richman, 2014)
Building Type Space Type
Maintained Average
Illuminance at Working
Level (lux)
Measurement
(Working) Height (1
meter = 3.3 feet)
Office Buildings
Single offices 400 At 0.8m
Open plan offices 400 At 0.8m
Conference rooms 300 At 0.8m
Table 6.5.1.2 Illumination Requirement of Different Activities (Richman, 2014)
Activity Illumination (lux)
Public areas with dark surroundings 20-50
Simple orientation for short visits 50-100
Working areas where visual tasks are
only occasionally performed
100-150
Warehouse, homes, theaters,
archives
150
Easy office work, classes 250
Normal office work, PC work, study
library, show rooms,
500
Supermarkets, mechanical
workshops, office landscapes
750
Normal drawing work, detailed
mechanical workshops, operation
theaters
1,000

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Detailed drawing work, very detailed
mechanical works
1500 - 2000
Performance of visual tasks of low
contrast and very small size for
prolonged periods of time
2000 -5000
Performance of very prolonged and
exacting visual tasks
5000 - 10000
Performance of very special visual
tasks of extremely low contrast and
small size
10000 - 20000
The standards and regulations on monitor screen are shown in Table 6.5.1.3.
Table 6.5.1.3 Work on Display Screen Equipment (DSE) or otherwise
Screen classes in
accordance with ISO
9241-7
I II III
Screen Quality good medium weak
Average luminances of
luminaires which are
reflected in the screen
≤ 1000 cd/m2
≤ 250 cd/m2
Table 6.5.1.4 Illuminating Engineering Society of North America (IESNA) Standard
Illuminance 500 lux (Horizontal) IESNA (2011)
Unified Glare Ratio ≤ 19 IESNA (2011)
Luminance Ratio
Task to immediate background
surface 3:1 (1:3)
IESNA (2011)
Task to dimmer(bright) distance
background 10:1 (1:10)
Paper task to negative (positive)
polarity VDT screen 3:1 (1:3)
Glare Ratio
Task to delight media 1:40, Task
to luminaires 1:40
IESNA (2011)
Light-source-adjacent-surfaces
to light source 1:20
6.5.2 Illuminance Level Analysis

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Illuminance level is total luminous flux incident on a surface, per unit area. In this project, indoor
illuminance level of type 2 model on winter solstice, summer solstice, and spring equinox are simulated
to represent heating, cooling, and transition season. On each day, 5 time points are simulated, which are
at 9AM, 11AM, 1PM, 3PM, and 5PM. The reason for choosing these 5 time points is in order to keep
consistency with the field experiment. The simulation results of Radiance are shown below. The
different between illuminance and luminance is shown in Figure 6.5.2.1.
Figure 6.5.2.1 Illuminance and Luminance (Ransen, 2014)
The light level images rendered by RADIANCE are shown in the following sections. In these images, the
pictures with red frame mean the recommended performance, which means a light level between 500 –
1000 lux based on Richman’s study. The numbers in orange font means the light level in this situation is
too high (over 1000 lux). The numbers in red font means the light level in this situation is good (500-
1000 lux). The numbers in dark red font means the light level in this situation is medium (250 – 500 lux).
The numbers in black font means the light level in this situation is low (less than 250 lux).
For each condition analyzed below, an interim recommendation is proposed based only on light level
consideration. For those recommendations, the meaning of different color is shown in the following
table 6.5.2.1.
Table 6.5.2.1 Description on Color Representing Light Level
fulfill both requirement on desk and
monitor
need tasklight on desk
need tasklight on monitor
need additional shading device

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need tasklight on both desk and monitor
Spring Illuminance Level Analysis under Clear Weather Condition
The figure 6.5.2.2 show the illuminance level on spring equinox day under sunny (clear) weather.
According to the standard referenced in table 6.5.1.1- 6.5.1.4, a light level lower than 200 lux is
considered too weak and between 500 lux and 1000 lux is considered comfortable. On monitor screen
(computer-based work), at 9AM, only blinds at positive 45 degree has a light level lower than
recommendation value of 500 lux. Control group at 9AM has an illuminance value over 1000 lux, which
is too bright for PC work. From 9AM to 11AM, all groups have a decrease on illuminance value except for
blinds at positive 45 degree. However, it still cannot reach the 500 lux line for the comfort level. Blinds
at closed position, at negative 45 degree positon, and tensioned shades also have a lower-than-500
illuminance value. At 11AM, fully opened blinds provide the best Illuminance value for visual comfort
among all groups. The light level of all groups keep decreasing after 11AM. Control group and blinds at
opened position have the best visual performance at 1PM. Other groups block too much sunlight and
artificial lighting is needed. At 3PM, only control group keeps light level over 500 lux. From 3PM to 5PM,
light level of all groups keeps decreasing and artificial lighting is needed even for control group.

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Figure 6.5.2.2 Light Level on Monitor, sunny, 03/21
For light level on desk (paper-based work), 500 lux is required according to IESNA. The simulation is
shown in Figure 6.5.2.3. At 9AM, blinds at opened / -45 degree position and tensioned shades provide
good visual environment. Indoor area becomes brighter from 9AM to 11AM. At 11AM, there is too much
light on desk of control group (over 1000 lux). Blinds at negative 45 degree provide daylight condition
for paper work at this time. The brightness on desk does not change much from 11AM to 1PM. Blinds at
negative 45 degree still works best on indoor visual environment during this time period. At 3PM, blinds
at opened position are the best skylight group among others. Light level of all groups decreases after
3PM. At 5PM, only control group can fulfill the minimum line of 500 lux although it is still a bit lower
than this value. Tensioned shades, blinds at closed position, and blinds at positive 45 degree is not
recommended to use on this day under clear weather condition since they block too much sunlight so
that additional artificial lighting is needed to maintain the 250 lux minimum requirement. When the
light level is under 250 lux, additional lighting is needed, and when the light level is between 250 and
500 lux, it is recommended for doing easy office works.

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Figure 6.5.2.3 Light Level on Desk, Sunny, 03/21
The figure shows the light level changes on monitor and desk from 9AM to 5PM under sunny weather in
spring. The light orange area means good for light level (500 – 1000 lux) and light red area means
medium for light level (250 to 500 lux).
Figure 6.5.2.4 Light Level Change, sunny, 03/21

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Interim Recommendation under sunny weather in spring
Spring, Sunny 9AM 10AM 11AM 12PM 1PM 2PM 3PM 4PM 5PM
Shades Close Open
Blinds -45 Open

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Spring Illuminance Level under Overcast Weather Condition
The following picture (Figure 6.5.2.5) shows the illuminance level on monitor screen on spring
equinox day under cloudy (overcast) weather. For light level analysis on monitor screen, at 9AM,
illuminance value of all groups is too low to conduct computer-based work. Among all these groups,
control group has the highest illuminance value and blinds at negative 45 degree have the lowest.
Light level of all groups increases from 9AM to 11AM. At 11AM, only control group can provide a
light level reaching the medium quality of brightness. Indoor visual performance at 1PM is generally
the same as at 11AM. Control group still is the only group can reach the medium lighting quality
among other groups although illuminance value of blinds at opened position, at positive/negative 45
degree, and tensioned shades both increased. From 1PM o 3PM, all groups have a decrease of light
level on monitor screen. Except for control group, additional artificial lighting is needed. Light level
on desk of all groups continues decreasing from 3PM to 5PM. At 5PM, additional lighting is
necessary for all groups since every group has an illuminance value lower than 200 lux.
Figure 6.5.2.5 Light Level on Monitor, Overcast, 03/21

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The following picture (Figure 6.5.2.6) shows the illuminance level on desk on spring equinox day
under cloudy (overcast) weather. At 9AM, both control group and blinds at opened position can
fulfill the requirement line of 500 lux for paper-based work. Light level on desk of all groups
increases from 9AM to 11AM. At 11AM, light level of control group is too bright (over 1000 lux).
Blinds at opened position and at negative 45 degree position provide a comfort visual
environment for paper-based work. From 11AM to 1PM, except for blinds at closed position and
at positive 45 degree position, illuminance value of other groups continues increasing. Control
group still has too much sunlight on desk at this time. Blinds at opened position and at negative
45 degree position keep providing a comfortable visual environment. Light level on desk
decreases from 1PM to 3PM for all groups except for blinds at closed position. However, its light
level is still too low for paper-based work at this time. Indoor visual performance of blinds at
opened position and negative 45 degree position remain the best among all group. From 3PM to
5PM, light level of all groups decreases. At 5PM, only control group and blinds at opened
position can provide enough light for easy office work.
Figure 3.5.2.6 Light Level on Desk, Overcast, 03/21

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Figure 6.5.2.7 Light Level Change, Overcast, 03/21
Interim Recommendation
Spring, Overcast 9AM 10AM 11AM 12PM 1PM 2PM 3PM 4PM 5PM
Shades Open Open Open
Blinds Open Open Open

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Summer Illuminance Level under Clear Weather Condition
The following picture (Figure 6.5.2.8) shows the illuminance level on monitor screen summer solstice
day under sunny (clear) weather. At 9AM, every group except for blinds at negative 45 degree position
fulfill visual requirement. At this time, control group has the highest light level on monitor screen. From
9AM to 11AM, blinds at closed position and tensioned shades have a decrease on light level, and other
groups have increase. Control group even has an illuminance value of 5841 lux, which is too bright for
computer-based work. At 11AM, light level of blinds at closed position and tensioned shades group is
still low. Blinds at positive and negative 45 degree groups provide the most comfortable visual
environment at 11AM. At 1PM, light level of control, blinds at opened position, at positive and negative
45 degree all reaches their peak value. Performance of blinds at negative 45 degree is the best for
computer work at this time point. From 1PM to 3PM, light level of all groups decreases. Only blinds at
negative 45 degree position can fulfill the requirement (with an illuminance value of 201 lux) at this
time. At 5PM, only control groups can meet the requirement.
Figure 6.5.2.8 Light Level on Monitor, Sunny, 06/21

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Figure 6.5.2.9. shows the illuminance level on desk on summer solstice day under sunny (clear) weather.
At 9AM, only blinds at negative 45 degree position and tensioned shades cannot meet the minimum
requirement of 500 lux. However, illuminance value of other groups is too high which can cause visual
discomfort. Besides, light level of tensioned shades is only slightly lower than 500 lux. Thus, tensioned
shades have the best visual performance at this time. At 11AM, control group, blinds at opened position,
and at negative 45 degree has extremely high light level on desk. Thus, shading device is needed at this
time. However, light levels of other groups are all lower than 500 lux. Additional task light is needed for
these three groups. At 1PM, light level of all groups is lower compared with at 11AM. The condition is
similar at 1PM and 3PM for all groups as at 11AM. Control group, blinds at opened and negative 45
degree position still have extremely high illuminance level and they all reach their peak light level at
1PM, and then start to decrease. Task light is recommended at this time period as well. At 5PM, control
group has an illuminance value of 670 lux, which can fulfill the visual comfort requirement for paper-
based work on horizontal level. At this time, no shading device is recommended.

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Figure 6.5.2.10 Light Level Change, Sunny, 06/21
Summer, Sunny 9AM 10AM 11AM 12PM 1PM 2PM 3PM 4PM 5PM
Shades Close Close Close Open
Blinds Closed 45 Closed Open

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Summer Illuminance Level under Overcast Weather Condition
Figure 6.5.2.11 shows the illuminance level on monitor screen on summer solstice day under cloudy
(overcast) weather. At 9AM, only control group and blinds at opened position can meet the
requirement for computer-based work. Light level on monitor screen of all groups increases after
9AM. At 11AM, besides control group and blinds at opened position, blinds at negative 45 degree
position also meet the requirement although all these groups only have a medium quality of
brightness. Condition at 1PM and 3PM is not much different compared with at 11AM. However,
since the illuminance value of blinds at negative 45 degree decrease a little. The light on screen of
this groups is a little weak for computer-based work. At 1PM, light level on monitor screen of
control group, blinds at opened position, and tensioned shades all reaches their peak value, and
then starts to decrease. At 5PM, only control group can meet the requirement.
For paper-based work (on desk), Figure 6.5.2.12 shows the daylight condition on summer solstice day
under overcast weather. At 9AM, three groups exceed the minimum value of 500 lux, control group,

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blinds at opened position, and blinds at negative 45 degree position. The light level on desk of control
group is too bright at 9AM. Except for blinds at closed position, every other group has an increase on
illuminance value from9AM to 11AM. At 11AM, both light level on desk of control group and blinds at
opened position is too high. Blinds at negative 45 degree position have the best visual performance at
this time point. At 1PM, control group, blinds at closed position, and blinds at negative 45 degree all
reach their highest illuminance value. Blinds at negative 45 degree position still perform best on desk
light level. After 1PM, illuminance value of all groups shows a decrease. The overall condition is similar
to 1PM at 3PM. At 3PM, both blinds at opened position and at negative 45 degree position is
recommended. At 5PM, due to the decrease of illuminance, control group now provides an acceptable
light level. Blinds at negative 45 degree cannot provide enough light at this time. Blinds at opened
position have the most comfortable visual environment at this time.

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Summer, Overcast 9AM 10AM 11AM 12PM 1PM 2PM 3PM 4PM 5PM
Shades Open
Blinds Open

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Winter Illuminance Level under Clear Weather Condition
Figure 6.5.2.14 shows the illuminance level on monitor screen on winter solstice day under sunny
(clear) weather. At 9AM, all groups can fulfill the visual requirement on light level for computer-
based work. Illuminance value of control group is little high compared with the standard value. At
11PM, all groups have the highest illuminance value on monitor screen during the day. Blinds at
positive 45 degree position have the largest increase compared to its value at 9AM. At this time,
light on monitor of control group is still too high to create comfortable visual environment for
occupant. At 1PM, light level of control group remains too high. Blinds at closed and negative 45
degree position, and tensioned shades cannot provide enough light on screen for computer-based
work. Blinds at opened position provide a relatively better visual environment compared with blinds
at positive 45 degree, though they both meet the requirement. At 3PM, only control group can meet
the requirement. Decrease on illuminance value continues after 3PM. At 5PM, additional lighting is
needed since no group has an illuminance value exceeding 100 lux.

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For paper-based work, Figure 6.5.2.15shows light level change on a sunny (clear) winter solstice day of
six groups. At 9AM, only control group has an illuminance value over 500 lux (850 lux). At 11AM, light
level of control group on horizontal level is too bright for paper-based work. Illuminance value of all the
other groups does not exceed 500 lux at this time. However, Blinds at closed and opened position both
have an illuminance value closed to 500 lux, which can be considered as providing a comfortable visual
environment. At 1PM, light level of all groups shows decrease compared with at 11AM. Only control
group can meet the standard. At 3PM, control group has a lower but closed to 500 lux illuminance value,
thus, no additional light is needed. After 3PM, additional artificial light is necessary.
Figure 6.5.2.15 Light Level on Desk, Sunny, 12/21

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Figure 6.5.2.16 Light Level Change, Sunny, 12/21
Winter, Sunny 9AM 10AM 11AM 12PM 1PM 2PM 3PM 4PM 5PM
Shades Open Close Open Open
Blinds Closed 45 Open Open

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Winter Illuminance Level under Overcast Weather Condition
Light level on monitor screen on winter solstice day under overcast weather is shown in figure
6.5.2.17. For the whole day, additional artificial lighting is needed. The control group has the highest
illuminance value among all 6 groups at every time point. Even the highest illuminance value of
control group at 1PM (188 lux) is still lower than 200 lux. Thus, no shading device is recommended
on winter solstice day under overcast weather condition and additional artificial light is needed for
all day.
Figure 6.5.2.17 Light Level on Monitor, Overcast, 12/21
Figure 6.5.2.18shows the illuminance level on desk on winter solstice day under overcast weather. At
9AM, both control group and blinds at opened position and negative 45 degree position have an

67
illuminance value exceeding 500 lux. Since illuminance value of control group (1128 lux) is a little bright
for paper-based work, blinds at opened or negative 45 degree position are preferred at this time. From
11AM till 3PM, blinds at negative 45 degree performances best among all groups. The general indoor
daylight condition is similar during this time period. At 5PM, control group and blinds at negative 45
degree position is recommended.
Figure 6.5.2.18 Light Level on Desk, 0vercast, 12/21

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Winter, Overcast 9AM 10AM 11AM 12PM 1PM 2PM 3PM 4PM 5PM
Shades Open Open
Blinds Open Open
6.5.3 Glare Analysis
6.5.3.1 Glare Analysis in Ecotect
Glare issue is that difficulty in seeing under direct or reflected bright light. A significant ratio between
task luminance and background luminance level will cause glare inside the room (Figure 6.5.3.1). This is
a main problem in skylight application since there will be more sunlight inside room through skylight.
Figure shows the cause of glare problem. Unified Glare Rating (UGR) and Daylight Glare Index (DGI) is
used to measure the level of glare. The following table shows maximum UGR value in different
environment.
Table 6.5.3.1 UGR Standard on Different Activities
Office interior type, task or activity UGR
Performance of work, copying, etc. 19
Writing, typing, and reading, data
processing on a PC
19
Technical drawing 16
CAD workstations 19
Conference and meeting rooms 19
Reception desks 22
Archives 25

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Figure 6.5.3.1 Cause of Glare (Ransen, 2014)
In order to do the glare analysis in RADIANCE, a fisheye camera is needed in Ecotect model.
The detailed process of creating fisheye camera is showed below (Figure 6.5.3.2):
 Under ‘Elements in Current Model’, create a new camera called ‘Camera_Fisheye’.
 Choose ‘Hemispherical’ as lens type.
 Change ‘Horizontal View Angel’ to 180 and ‘Vertical View Angel’ to 180.
 Finish creating by clicking ‘Add New Element’.
Figure 6.5.3.2 Fisheye Setting in Ecotect
The rendering process is basically the same as light level simulation described before. The difference is
to choose ‘Luminance Image’ instead of ‘Illuminance Image’. For glare analysis, only situation under
sunny weather on spring equinox day, summer and winter solstice day is considered.
After finish the rendering, UGI is calculated in RADIANCE. Following command is used for calculation.
 Use command ‘cd Desktop’ to access Desktop
 Use command ‘cd Glare’ to access Glare folder

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 Use command ‘dir/w’ to see the list of filed in this folder
 Use command ‘findglare –p fisheye_c1.pic > glare.glr’ to make a glr.file to be able to calculate
UGR value
 Use command ‘glarendx –t dgi glare.glr’ to do the calculation
The same method is used for daylight glare index (DGI) calculation.
In this section, all the images with yellow boarding means there is glare issue under this condition, the
UGR or DGI value is over 19.
Glare Analysis (UGR) on Spring Equinox Day
Figure 6.5.3.3 shows fisheye image of indoor visual performance on monitor on spring equinox day. At
9AM, control group, shades group, and blinds at negative 45 degree position group show no glare
problems. At this time, shading device is not needed. At 11AM, UGR of control group increase to 21. It is
recommended to set blinds panel position to negative 45 degree since it is the only group without glare
at this time. At 1PM, the recommendation is the same as at 11AM. At 3PM, blinds is recommended to
be fully closed or remain negative 45 degree position as earlier. At 5PM, no shading device is needed
since control group now has a UGR lower than 19.

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Figure 6.5.3.3 Glare Analysis on Monitor, 03/21
Simulation result on desk level is shown in Figure 6.5.3.4. On the desk, at 9AM, no shading device is
needed since even control group has a UGR value of 4. At 11PM, the UGR value of control groups
increases significantly to 24. At this time, no group can efficiently prevent glare. The lowest UGR value at
this time is still 21, of blinds at negative 45 degree position. Thus, additional shading device is suggested.
At 1PM, only tensioned shades can fulfill the requirement. The condition at 3PM is basically the same as
at 1PM. Tensioned shades and blinds at negative 45 degree position are two groups can prevent glare.
At 5PM, no group has a UGR value larger than 12, thus, no shading device is needed at this time.

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Figure 6.5.3.4 Glare Analysis on Desk, 03/21
Interim Recommendation:
Spring 9AM 10AM 11AM 12PM 1PM 2PM 3PM 4PM 5PM
Shades Close Close Close
Blinds -45 -45 -45

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Glare Analysis (UGR) on Summer Solstice Day
Figure 6.5.3.5 shows fisheye image of indoor visual performance on monitor on summer solstice day. At
9AM, except for blinds at fully opened position and positive 45 degree position, UGR value of all the
other groups does not exceed the maximum value of 19. From 11AM to 3PM, only blinds at fully closed
position and shades fulfill the standards. At 5PM, only UGR value of blinds at positive 45 degree exceeds
the maximum value. Generally, blinds at fully closed position and tensioned shades have the best ability
to prevent glare on monitor screen compared with other groups.

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Simulation result on desk level is shown in Figure 6.5.3.6. On desk, the UGR values of all groups are
much higher than on monitor. At 9AM, control group, blinds at negative 45 degree position group, and
shades group all have a UGR value less than 19. At 11AM, all the groups can’t meet the requirement. At
1PM, only tensioned shades have a UGR value fulfilling the standards. The UGR values of all the groups
decrease after 1PM, however, at 3PM, still only tensioned shades has a value less than 19. At 5PM, all
groups can meet the standards requirement. At this time, no shading is needed for preventing glare. In
general, tensioned shades have the best performance on preventing glare on desk in summer.

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Interim Recommendation:
Summer 9AM 10AM 11AM 12PM 1PM 2PM 3PM 4PM 5PM
Shades Close
Blinds Closed Closed

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Glare Analysis (UGR) on Winter Solstice Day
In winter, performance at 5PM is not considered since at that time artificial lighting is needed and no
glare issue is found at that time either. Besides, glare issue is much more serious in winter compared
with summer since sun angle in winter is lower than in summer. With lower sun angle, more sun light is
reflected off the earth also at a lower angle, which causes more glare visible from the surface. When
sun angle is higher, the light has a more vertical angle and less glare is created.
Simulation result on monitor level is shown in Figure 6.5.3.7. From 9AM to 1PM, UGR values of all
groups exceed maximum value of 19 except for blinds at positive/negative 45 degree position. At 11AM
and 1PM, UGR values of control group, blinds at fully opened position, and blinds at positive position
even reach about 60. At 3PM, except for tensioned shades and blinds at positive 45 degree, other
groups can fulfill the standard. Compared among different groups, fully opened blinds can cause the
most serious glare problem even compared with no shading group. Blinds at negative 45 degree and
tensioned shades generally can prevent most of the glare during the day. Additional shading device is
needed from 11AM to 1PM as a combination with tensioned shades or venetian blinds.

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Simulation result on desk level is shown in Figure 6.5.3.8. Glare problem on desk (horizontal level) is
much less serious than on monitor screen (vertical level). For the whole day, there is no glare problem
for all groups.

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Winter 9AM 10AM 11AM 12PM 1PM 2PM 3PM 4PM 5PM
Shades Close
Blinds Closed
Glare Analysis (DGI) on Spring Equinox Day
Daylight glare index (DGI) analysis on spring equinox day is shown in figure 6.5.3.9. From 9AM to 11AM,
no shading device is needed since DGI value of control group does not exceed the maximum value of 19.
It is noticed that due to the reflection of blinds panel, blinds at positive 45 degree position keeps having
the highest DGI value among all 6 groups. Thus, this panel angle should be avoided on this day under
clear weather. From 1PM to 3PM, blinds at open position, blinds at negative 45 degree position, and
tensioned shades is recommended. After 3PM, since DGI value is no longer larger than 19, no shading
device is needed.

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Figure 6.5.3.9 DGI on Monitor, 03/21
Glare Analysis (DGI) on Summer Solstice Day
Figure 6.5.3.10 shows the DGI analysis on summer solstice day. The glare issue is less serious in summer
than in winter. From 9AM to 5PM, control group remains a DGI value lower than 19 all the time. For all
groups during the whole, there is no group having a DGI value higher than 19.

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Glare Analysis (DGI) on Winter Solstice Day
Simulation result on monitor level is shown in Figure 6.5.3.11. Glare problems is much more serious in
winter compared with in spring and summer due to the higher sun angle as mentioned before. For
control group, at 11AM, the DGI value even reaches 37. Thus, shading device is necessary on this day. At
9AM, blinds at opened, positive 45 degree, and negative 45 degree all can efficiently prevent glare. Due
to sun angle and panel reflection, from 11AM to 3PM, blinds at opened position and positive 45 degree
position both have a very high DGI value around 35. During this time period, only tensioned shades can

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keep a DGI value lower than 19. Thus, it is suggested to use tensioned shades from 11AM to 3PM. There
is no need for shading device after 3PM since the highest DGI value at 3PM is 19 of blinds at positive 45
degree position.

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