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Chromogenic Windows

Findings #10, March 2014

 

Chromogenic windows tint automatically based on outside temperature and brightness, or as determined by automated building controls. In an evaluation in Denver, Colorado, chromogenic windows significantly reduced heat gain over the baseline low-e window, reducing annual HVAC cooling electricity use by as much as 10%. Click on the infographic below to enlarge.

GPG Findings 10, March 2014, Electrochromic and Thermochromic Windows. Opportunity: How much energy can be saved by daylighting U.S. office buildings? 1 billion MBTU of lighting energy can be saved by taking advantage of daylight. Technology: How to chromogenic windows save energy? Reduce solar heat gain by transitioning dynamically from clear to dark. Electrochromic (EC) use switches or automated building control systems to actively tint windows via electric current. Thermochromic (TC) use adhesive coating to adjust tinting passively with window surface temperature. Measurement and Verification: How did chromogenic windows perform in M and V compared to baseline low-e windows? 9-10% energy savings. 48-50% reduction in heat gain. Preserved views. EC tinted to dark blue; TC performance sensitive to surrounding surface geometry. Captured benefit of natural daylighting. Provided less glare. Deployment: Where does M and V recommend deploying chromogenic windows? Further evaluation. GSA is undertaking further evaluation of EC Windows in high-rise curtain wall applications with lighting that adjusts in response to daylight.


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