Heating Windows

In recent years, window technology has improved dramatically, resulting in lowered energy bills. Some of the most important energy saving features of windows include:

multiple layers of glazing,
thickness of air space between in double-glazed windows,
low conductivity gas fill in sealed insulated glass windows,
tinted glass coatings, and
low-emissivity (low-e) coatings.

Purchasing Tips

When shopping for new windows, look for the National Fenestration Rating Council label; it means the window’s performance has been certified.
The lower the U-value, the better the insulation. In colder climates, a U-value of 0.35 or below is recommended. These windows have at least double glazing and low-e coating.
In warm climates, where summertime heat gain is the main concern, look for windows with double glazing and spectrally selective coatings that reduce gain.
Select windows with air leakage ratings of 0.3 cubic feet per minute or less.
In temperate climates with both heating and cooling seasons, select windows with both low U-values and low solar heat gain coefficiency to maximize energy benefits.

Resources

National Fenestration Rating Council, (301) 589-6374, www.nfrc.org
National Wood Window and Door Association, (800) 223-2301, www.nwwda.org
American Architectural Manufacturers Association, (847) 303-5664, www.aamanet.org