Project Poster_Chen Hu
Transcript of Project Poster_Chen Hu
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 devices on skylights in the IW Living laboratory. Skylights were separated with a 1” thick material to identify the performance 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 skylights can provide passive solar heat gain and daylight, 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
The Lutron Tensioned Shade is specifically designed for skylights and tilted windows, 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 SimulationA 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, Retrosolar venetian blind, and Lutron tensioned shade. In addition, Four different 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 oF 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