Sage Electrochromics calls its new SageGlass Triple Pane the world’s most energy-efficient glass. That’s a bold claim, but the product is an impressive bit of technology. The triple-pane, gas-filled glazing comes with an electrochromic coating that takes on a dark tint when charged with a weak DC current. The user controls the amount of tint via a wall-mounted dimmer.
Product manufacturer Sage Electrochromics has had switchable glass for several years. What’s new is the marriage of that technology with the most efficient window glass, with an insulating value of more than R-8 (that’s a U-value of .12) compared to R-3 for a typical low-E double pane.
The switchable layer doesn’t affect insulating value but rather lets users control the radiant heat and visible light that gets through. According to Helen Sanders, Sage’s VP of Technical Business Development, SageGlass in its highest-performing configuration lets user vary visible light transmission from 52% in the clear state to 3% when fully tinted. Even with just 3% of light getting through, the window doesn’t go opaque. “This is not privacy glass,” says Sanders. “It’s more like a pair of very dark sunglasses.”
Going from clear to dark also varies Solar Heat Gain Coefficient – the percentage of radiant solar heat the glass lets through – from 0.38 in the clear state to 0.05 when filly tinted. By comparison, the company’s switchable double-glazed product offers a SHGC range of .48 to .09.
The big customers for this product are commercial glazing contractors, but it’s also being sold to window companies for high-end residential products. For instance Marvin offers the glass as an option on a limited number of its stationary units.
The new glass could really earn its keep on East and West facing facades, where low sun angles defeat overhangs. The glass itself costs more than a standard triple-pane but Sanders says it’s more accurate to compare window systems, since the ability to tint eliminates the need for exterior shading and interior blinds. “It’s a solution to solution comparison,” she says.