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Title: Energy and visual comfort performance of electrochromic windowswith overhangs

Abstract

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 commercialmore » 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.« less

Authors:
;
Publication Date:
Research Org.:
Ernest Orlando Lawrence Berkeley NationalLaboratory, Berkeley, CA (US)
Sponsoring Org.:
USDOE. Assistant Secretary of Energy Efficiency andRenewable Energy. Office of Building Technologies; Scientific ResearchCouncil of Turkey (TUBITAK) through NATO-B2 FellowshipProgram
OSTI Identifier:
924851
Report Number(s):
LBNL-59064
Journal ID: ISSN 0360-1323; BUENDB; R&D Project: 0; BnR: YN0100000; TRN: US200809%%592
DOE Contract Number:  
DE-AC02-05CH11231
Resource Type:
Journal Article
Resource Relation:
Journal Name: Building and Environment; Journal Volume: 42; Journal Issue: 6; Related Information: Journal Publication Date: June 2007
Country of Publication:
United States
Language:
English
Subject:
32; APERTURES; CLIMATES; COMMERCIAL BUILDINGS; CONFIGURATION; CONTROL SYSTEMS; DAYLIGHTING; DESIGN; ENERGY EFFICIENCY; GLASS; ILLUMINANCE; PERFORMANCE; SHADING; SOLAR RADIATION; SUN; WINDOWS

Citation Formats

Lee, E.S., and Tavil, A.. Energy and visual comfort performance of electrochromic windowswith overhangs. United States: N. p., 2005. Web.
Lee, E.S., & Tavil, A.. Energy and visual comfort performance of electrochromic windowswith overhangs. United States.
Lee, E.S., and Tavil, A.. Thu . "Energy and visual comfort performance of electrochromic windowswith overhangs". United States. doi:. https://www.osti.gov/servlets/purl/924851.
@article{osti_924851,
title = {Energy and visual comfort performance of electrochromic windowswith overhangs},
author = {Lee, E.S. and Tavil, A.},
abstractNote = {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.},
doi = {},
journal = {Building and Environment},
number = 6,
volume = 42,
place = {United States},
year = {Thu Nov 03 00:00:00 EST 2005},
month = {Thu Nov 03 00:00:00 EST 2005}
}