Understanding Windows in High-Performance Envelopes

Windows are not low-hanging fruit when it comes to energy efficiency, but they're certainly an important part of the mix. What has struck me as I've listened to how different projects ran the energy models on significant envelope renovations is how all the different factors interplay. There is no across-the-board best window system — there is only the best system for your facility's orientation, and percentage of glazing, and thermal massing, and level of insulation, and shading system, and on.

"There is no universal replacement when it comes to windows; one size does not fit all," according to a recent Building Operating Management article on high-performance windows. "Options today include the number of glazings installed, the use of an inert gas between the glazings, the application of a reflective coating or film to the glazing the use of a low-e glazing to reduce radiant heat loss, the use of internal or external shading devices, and the type of materials used to construct the window frame."

If you're getting ready to embark on an upgrade to your window system (or you just want to better understand what's going on at the perimeter), check out the article. It breaks down high-performance window systems by individual factors to show how they can interact to improve the efficiency of the building envelope. You can find it at www.facilitiesnet.com/16788bom.

I'd love to hear about your window retrofit project. How did it go? Any surprises? Let me know in the comments below.

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