Sage Electrochromics, Inc. produces an electronically tintable glass that can be very useful in green building applications. The company recently received a $72 million Department of Energy (DOE) conditional commitment for loan guarantee through an Energy Policy Act of 2005 program and $31 million Advanced Energy Manufacturing Tax Credit from a program established under the American Recovery and Reinvestment Act of 2009.

Sage produces one product… the appropriately named SageGlass. As stated in the description above, it is an electronically tintable glass, similar to those self-tinting eyeglasses you’ll see nowadays, but these are for use in building windows and skylights, and can be switched from clear to darkly tinted at the click of a button, or programmed to respond to changing sunlight and heat conditions. Sage states that ‘energy consumption and costs are reduced significantly’ and if this product really works like it’s advertised I agree that it will indeed save energy. In fact, according to the National Renewable Energy Laboratory (NREL), electrochromic windows could save one-eighth of all energy used by U.S. buildings each year, equivalent to about 5% of the nation’s total energy budget.

SageGlass uses a multi-layer, thin-film tungsten-oxide coating. To me, that doesn’t have a ton of significance right off the bat, but when I read that it’s “as durable as low-emissivity coatings” that’s getting more into my realm of understanding.

But of course it takes energy to switch the glass. The glazing initially uses 0.28 W/ft2 to switch the glass from clear to tinted, which takes several minutes, and utilizes 0.1 W/ft2 to maintain the tint. According to the company, “with typical clear glass in an insulated glazing unit, SageGlass reduces the visible transmittance from 62% to 3.5% while reducing the solar heat gain coefficient from 0.48 to 0.09”. That’s significant, on the scale of reducing required annual energy costs for an IECC 2009-compliant 15,000 ft2 square office building located in Chicago (with lots of other assumptions) by $1,090/yr.

Sage is currently working with various window, skylight, and curtainwall manufacturers to produce both commercial and residential products with this type of tintable control option, though it’s already available through several vendors and installed in both commercial, educational and residential properties.

The product is almost certainly cost-prohibitive at this point, on the order of 6-7x cost adds, but in time I could definitely see this becoming more of a widespread option. Sage thinks so too, expecting the cost to eventually become competitive with standard high-performance glazing combined with interior mechanized shades.

Bottom line, SageGlass and other similar products can provide energy savings, control peak electricity demand and contribute to an overall improved indoor environment through light quality and quantity (glare) control.

 

Use of Sage Electrochromics SagegGlass may contribute to the following credits:

EA Credit 1 - Optimize Energy Performance
EQ Credit 6 - Controllability of Systems
EQ Credit 7 - Thermal Comfort
EQ Credit 8 - Daylight and Views

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