Smart Windows Save Energy

November 30, 2010

Windows have gone high tech with the availability of SageGlass electrochromic glass.  Now designers and owners can use window shading to save energy in real time.  As the pictures above from Ball State show, SageGlass windows can be clear or tinted, depending on exterior light levels and interior light requirements.

How It Works

Electrochromic glass is made by coating the inside of the exterior glass pane with many layers of thin film ceramics.  These ceramics are clear in their natural state, but when electricity flows through the layers, the ions become excited and each layer becomes darker, providing light shading and solar heat protection similar to a low-e coating.  As more layers are activated, the glass gets darker and provides more protection while maintaining its translucence.

Conversely, the flow of electricity can be lowered so the glass becomes lighter, returning to its normal clearness.  This allows building spaces to use daylight harvesting and heat gain to their benefit.

Zone controls can be installed according to the needs of the occupants.  Clerestory or upper windows might remain clear, even if there is direct sunlight, in order to harvest daylight.  Likewise, areas with special needs, such as those set up for audio/visual displays, can use switches to override the zonal controls. 

Energy Savings

SageGlass saves money on construction and design costs, reduces energy use, and does not have a substantial cost premium. 

  • Mechanical systems can be downsized due to lower heating and cooling requirements, saving 20-25% on the cost of the system. 
  • Exterior sunshades can be eliminated from the design. 
  • Buildings can see energy savings of 20-40% based on down-sized mechanical systems and reduced lighting requirements.
  • The peak energy load can be reduced by 25-30%. 
  • SageGlass costs more than traditional storefront glass, but the savings above help offset these up-front charges. 
  • The energy required to run a system of 1500 square feet of glass is approximately that of a 60 watt incandescent bulb.

“Smart glass” has the capability to revolutionize how buildings are designed.  Modern building designs make extensive use of glazing, cutting down on the efficiency of the buildings.  However, if the glazing system is able to respond in real time to the conditions outside, it could substantially reduce the size of mechanical systems and the amount of lighting required, saving building owners in design, construction, and operational costs.

Photos courtesy of SageGlass, copyrighted by Susan Fleck Photography and Gallop Studio.


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Dawn Killough

has over 15 years experience in the construction industry and is the author of Green Building Design 101, an e-book available from Amazon. She is a LEED AP and Certified Green Building Advisor, and has worked on the LEED Certification of three projects in Salem, Oregon.  
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