02703nas a2200205 4500008004100000245008300041210006900124260001200193300001400205490000700219520204000226653002402266653002302290653001602313653002702329653002202356100002102378700001902399856007902418 2007 eng d00aEnergy and visual comfort performance of electrochromic windows with overhangs0 aEnergy and visual comfort performance of electrochromic windows  c06/2007 a2439-24490 v423 a

DOE-2 building energy simulations were conducted to determine if there were practical architectural and control strategy solutions that would enable electrochromic (EC) windows to significantly improve visual comfort without eroding energy-efficiency benefits. EC windows were combined with overhangs since opaque overhangs provide protection from direct sun which EC windows are unable to do alone. The window wall was divided into an upper and lower aperture so that various combinations of overhang position and control strategies could be considered. The overhang was positioned either at the top of the upper window aperture or between the upper and lower apertures. Overhang depth was varied. EC control strategies were fully bleached at all times, modulated based on incident vertical solar radiation limits, or modulated to meet the design work plane illuminance with daylight. The EC performance was compared to a state-of-the-art spectrally selective low-e window with the same divided window wall, window size, and overhang as the EC configuration. The reference window was also combined with an interior shade which was manually deployed to control glare and direct sun. Both systems had the same daylighting control system to dim the electric lighting. Results were given for south-facing private offices in a typical commercial building.

In hot and cold climates such as Houston and Chicago, EC windows with overhangs can significantly reduce the average annual daylight glare index (DGI) and deliver significant annual energy use savings if the window area is large. Total primary annual energy use was increased by 2-5% for moderate-area windows in either climate but decreased by 10% in Chicago and 5% in Houston for large-area windows. Peak electric demand can be reduced by 7-8% for moderate-area windows and by 14-16% for large-area windows in either climate. Energy and peak demand reductions can be significantly greater if the reference case does not have exterior shading or state-of-the-art glass.

10abuilding simulation10aControl algorithms10adaylighting10aElectrochromic windows10aenergy efficiency1 aLee, Eleanor, S.1 aTavil, Aslihan uhttps://facades.lbl.gov/publications/energy-and-visual-comfort-performance01648nas a2200121 4500008004100000050001500041245007000056210006900126520122000195100001901415700002101434856007101455 2006 eng d aLBNL-6113700aEffects of Overhangs on the Performance of Electrochromic Windows0 aEffects of Overhangs on the Performance of Electrochromic Window3 a

In this study, various facade designs with overhangs combined with electrochromic (EC) window control strategies were modeled for a typical commercial office building in a hot and cold climate using the DOE 2.1E building energy simulation program. EC windows were combined with overhangs since opaque overhangs provide protection from direct sun which EC windows are unable to do alone. The window wall was divided into an upper and lower aperture so that various combinations of overhang position and control strategies could be considered. The overhang was positioned either at the top of the upper window aperture or between the upper and lower apertures. Overhang depth was varied. EC control strategies were fully bleached at all times, modulated based on incident vertical solar radiation limits, or modulated to meet the design work plane illuminance with daylight. Annual total energy use (ATE), peak electric demand (PED), average daylight illuminance (DI), and daylight glare index (DGI) for south-facing private offices were computed and compared to determine which combinations of façade design and control strategies yielded the greatest energy efficiency, daylight amenity, and visual comfort.

1 aTavil, Aslihan1 aLee, Eleanor, S. uhttps://facades.lbl.gov/publications/effects-overhangs-performance01044nas a2200133 4500008004100000050001500041245008000056210006900136260002500205520056300230100001900793700002100812856007700833 2005 eng d aLBNL-5702000aThe Impact of Overhang Designs on the Performance of Electrochromic Windows0 aImpact of Overhang Designs on the Performance of Electrochromic  aOrlando, FLc08/20053 a

In this study, various facade designs with overhangs combined with electrochromic window control strategies were modeled with a prototypical commercial office building in a hot and cold climate using the DOE 2.1E building energy simulation program. Annual total energy use (ATE), peak electric demand (PED), average daylight illuminance (DI), and daylight glare index (DGI) were computed and compared to determine which combinations of façade design and control strategies yielded the greatest energy efficiency, daylight amenity, and visual comfort.

1 aTavil, Aslihan1 aLee, Eleanor, S. uhttps://facades.lbl.gov/publications/impact-overhang-designs-performance