Windows cost building owners billions of dollars per year in energy, maintenance, and repair. But you should look at your glazing with a glass half full mentality. "Windows have the technical potential to be net energy suppliers to virtually all buildings in all climates," says Stephen Sel-kowitz, group leader of the windows and envelope materials group in the Building Technology and Urban Systems Derpart-ment of Lawrence Berkeley National Laboratory. "But that requires matching the right technology with the right design." Consider the following factors to make sure your windows are working for you. Clues for Replacement A full-scale retrofit of the glazing system is rarely justified by energy savings alone. Window replacement usually follows certain red flags. "If the glass is fogging up or the seals around it are broken, then it's time to replace your system. The windows are reaching the end of their useful life if they haven't already," says John Carmody, director of University of Minnesota's Center for Sustainable Building Research. "Once you decide to make the investment, that's when you should look carefully at the most efficient windows." Other meaningful warning signs come from occupant complaints. "The two major concerns that people report are glare and thermal comfort," explains Colin Blackford, regional technical advisor with manufacturer Guardian Industries. "Eventually there will be an opportunity to dramatically increase occupant satisfaction and energy performance by upgrading glazing."
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