EC Window Demonstration for General Office Space

GPG-033, November 2017

Electrochromic (EC) windows adjust their tint—and, thereby, the amount of light, glare and heat they allow into a room—dynamically. To assess tenant acceptance of EC windows in buildings with glass curtain-wall façades, the Lawrence Berkeley National Laboratory evaluated two different test-bed installations of EC technology—one in Portland, Oregon, the other in Sacramento, California. Click on the infographic below to enlarge.

GPG Findings 033, November 2017, EC window demonstration 
  in general office space. Opportunity: What have previous studies demonstrated about the potential for electrochromic (EC) windows?  reduced cooling energy, 48% reduction in heat gain. lighting energy with Advanced Lighting Controls; 
  Glare below the perceptible threshold. Technology: How do EC windows work? WINDOWS TINT IN responSE to external conditions or user override. Measurement and Verification. Where did M and V occur? Lawrence Berkeley National Laboratory assessed occupant satisfaction with EC windows in two buildings with curtain-wall construction—the 911 Federal Building in Portland, Oregon and the John E. Moss Federal Building in Sacramento, California. Results: How did 
  EC windows perform in M&V? 63-92%
  occupant preference over existing low-e.
  Implementations that both satisfy occupants and meet competing performance requirements are challenging and take time. CONTROL
  baseline conditions 
  AND occupant behavior DETERMINE SAVINGS
  In Sacramento, most blinds remained lowered and darker tint levels predominated, resulting in a 62% increase in lighting energy. In Portland, 40% more blinds were left raised and lighter tint levels predominated, resulting in 36% lighting energy savings but a 2% HVAC increase. NOT COST-EFFECTIVE FOR GENeral office space based on energy savings alone.
  Energy savings did not cover increased costs—in Portland, the incremental difference between installing spectrally selective low-e windows and EC windows was $37/ft2.Deployment: WWhere does 
  M&V recommend considering 
  EC windows? facilities where outside views are CRITICAL 
  A previous GPG study recommended EC windows where glare control is required but blinds would interfere with mission, such as Land Ports of Entry. 
  EC windows also could enhance architectural features that provide a connection with the outdoors, such as skylights and atriums, though this has not been evaluated. [PDF - 254 KB]

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