Selecting Low-E Windows Northampton MA

Source: REMODELING Magazine
Publication date: September 1, 2006

By Clayton DeKorne

Low-E glazing is marketed under a variety of names: SunBlocker, Sun-Coat, SunGate, and ComfortGlaze to name a few. Although it's clear that these products have something to do with energy efficiency, the name doesn't really tell how one might perform compared to another.

“Low-E coatings are certainly not all the same,” says Steve Easley, a building-science consultant based in Danforth, Calif. “How manufacturers use low-E technology varies.” Standard low-E coatings do a good job of reducing heat loss by reflecting heat back into a room, Easley says. A window with this coating would be a good choice when there is little concern about summer air-conditioning costs. But wherever air conditioning is used for a substantial portion of the year, windows need spectrally selective low-E coatings.

Spectrally selective coatings let most visible light through but block the shorter wavelength infrared solar heat waves, which greatly improves summer performance. These windows also block a considerable amount of the ultraviolet light that can fade fabrics and other interior finishes.

The only reliable way to choose a window based on energy performance is to pay close attention to the window sticker, Easley says. The National Fenestration Ratings Council (NFRC) has established clear standards for window performance.

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