Evaluating Energy Efficiency

You can't judge a window's efficiency just by looking at it. Fortunately, most new windows sold in the United States carry a label from the National Fenestration Rating Council, a nonprofit organization that certifies energy performance. The label shows how the window performs in three key areas.

If puzzling through the label is daunting, the EPA's Energy Star program makes judging efficiency easier. An Energy Star sticker means a window has met the minimum standard for insulating ability specifically for the climate of the region where it's sold. Energy Star windows generally exceed building code requirements and cost about 15 percent more than windows without the rating.

You can also go to http://windows.lbl.gov and download a program called Resfen. The software, which is free (PC-compatible only), lets you calculate how windows with different glazing systems and frame materials will affect your energy bill.

Understanding Window Ratings

Window glazing is rated on three criteria: how well it insulates, how much light it lets through, and how effectively it blocks heat from the sun. By taking these values into account, you can choose the best windows for your climate, and even tailor windows for specific rooms in your house.
Ask TOH users about Windows

Contribute to This Story Below