1. Dynamic Shading of Skylight Improves Indoor
Office Environment
Abstract Experiment Set up
Howard Wu, Chen Hu, Angela Kolosky
Advisors: Erica Cochran, Flore Marion
Vivian Loftness, Azizan Aziz, Bertrand Lasternas
Glare
Analysis
Surface Temp. Analysis
Dynamic skylights and shading devices provide multiple
energy and occupant benefits. To document the benefits, a
field experiment was conducted in the Intelligent Workplace
(IW) on CMU’s campus. The team installed multiple shading
devicesonskylightsintheIWLivinglaboratory. Skylightswere
separatedwitha1”thickmaterialtoidentifytheperformance
benefits of each skylight bay. To document and analyze the
benefits, the team measured radiant temperature, ambient
temperature, lighting intensity, relative humidity, outdoor air
temperature, weather conditions, glare, and occupant level
temperature and lighting intensity. The results show that
skylightscanprovidepassivesolarheatgainanddaylight,and
shadings can provide night insulation and reduce excessive
heat gain.
Performance Analysis
We analyzed the measured data in MS excel in order to compare and identify the best solution for
skylight shading. First, we classified the data according to weather condition, daytime & nighttime.
Next, we developed a metric to develop an optimal strategy to promote building performance.
The skylights evaluated are all southwest-oriented. In northern hemisphere,
the south-facing windows will receive most sunlight and passive heat gain,
comparing to other orientations. Generally, if the skylight is designed for both
daylighting and passive heat gain, it will be oriented to the South.
The RETROSolar venetian blinds is a
W-shaped louvers which reflect the
summer sunlight out and winter sunlight
into the building, which protect the
building from overheating but provide
passive solar in winter at the same time.
www.koester-lichtplanung.de
TheLutronTensionedShadeisspecifically
designedforskylightsandtiltedwindows,
the shade remains parallel to windows
with minimal sag in various angles, there
are also remote control that makes the
adjustments more convenient.
Model Developed by Russell Harmon
Computer Simulation
A computer simulation based on the field test is conducted using the softwares Ecotect
and Radiance to quantify impacts of shading devices on light levels and glare. The
evaluation on indoor visual performance is based on output illuminance images from
the softwares. The same bay is analyzed with 3 different shading strategies: no-shading
device,Retrosolarvenetianblind,andLutrontensionedshade.Inaddition,Fourdifferent
blinds positions (fully closed, positive 45, negtive 45, and fully opened) are simulated to
better achieve dynamic strategy. Heating, cooling, and transition season are simulated
under sunny and overcast weather condition, respectively. Preliminary result shows
that for both summer and winter, skylight with roller shades is the best to prevent glare,
and for blinds at various angle, negative 45 is optimal to prevent glare. For providing
a comfortable light level for paper based work, shades works better in summer and
blinds at fully open position works better in winter under sunny weather.
The skylight team used HOBO data
loggers and Globe Thermometers to
measure temperature, lighting intensity
and relative humidity. We also used FLIR
Infrared Camera, Fisheye lens to analyze
surface temperature and glare.
The pictures are from 5 PM of 03/17/2014. The average temperature of three bays
were almost same at 9 am and then began to increase. Since the air gap between
blind/shade and glazing trapped solar heat, these two bays reached a higher
temperature compared with control bay at 1 pm. At 1 pm, three bays all reached their
temperature peak. The average temperature of three bays have decreased from 1 PM.
At 5 PM, three bays almost had same temperature and remained this temperature till
7 PM. In conclusion, the high performance mesh shades kept the surface 10 o
F warmer
than the control bay with no shading thereby decreasing the heating load.
The above pictures show glare condition of three bays. From two light
contrast diagram, it is shown that contral has a severe glare problem.
Compared with Control Bay, other two bays show a slighter glare condition.
For monitor, blind and shade bay comply glare requirement for the whole
day and control bay only complies in afternoon. For background, Control Bay
excess requirement for the whole day. Based on this, it is recommended to
use shade or blind in morning.
Under overcast weather, blinds at negative 45
performs better both in summer and winter. Next
steps consist in developing an optimal daily dynam-
ic algorithm for the venetian blinds and tensioned
shades.
Fully Closed
Fully Open
Negative 45
Positive 45
Skylight