Types of Energy Efficient Windows: How to Choose the Best Windows

Low-cost windows can be pricier than they first appear. Like any weak link in the building envelope, poor-performing windows require a larger HVAC system and ducting, which is pricier up front and also more costly in the long run. “With insulating values as low as U-0.18, windows can have a huge impact on a home’s energy efficiency rating and a cascade effect on the cost of the overall project,” said Brett Dillon, a longtime builder and developer in Texas, who chairs the technical standards committee for ResNet, a nonprofit that trains and rates residential energy auditors.

The math is easy, but not all builders and homeowners respond to it. “A lot of people don’t know how much they pay for energy and don’t really care,” Dillon says. “But everyone cares about comfort.” By the time a new homeowner complains about drafty windows, condensation, or rooms that overheat in summer, it’s too late to rip out underperforming windows. Often the builder’s or homeowner’s solution is to upgrade the entire heating and cooling system. Interestingly, complaints about draftiness can usually be traced to low-quality windows with cold glass, not air leakage, says Steve Baczek, an architect outside Boston. “People say, ‘This window feels drafty,’ but it’s really not a draft. The radiation rate of the window is too high and you feel the cold,” he says. “It’s the same reason that basements feel cool. Your body is losing heat at a much higher rate as it tries to warm the cold walls.”