Energy Star Window Ratings: Eco-Friendly Savings

January 09, 2010

The Energy Star window rating system was created by a government dream team, at least when it comes to windows. The Environmental Protection Agency (EPA) and the Department of Energy (DOE) worked together to develop these window glass ratings, which means that not only are they energy efficient, but they're also eco-friendly. Energy efficiency means energy savings, and that savings comes right off your power bill and goes into your pocket.

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Energy Star Windows: What the Ratings Mean

Energy Star works with the National Fenestration Rating Council (NFRC), the most trusted name in window glass ratings in the country. The result is a label on all Energy Star windows that has a number of ratings listed on it. Here's a breakdown:

  • U-Factor: The U-Factor window glass rating is a measurement of heat transfer. The lower the U-Factor, the better the window insulates your home. They generally range from 1.25 down to 0.25.
  • Solar Heat Gain Coefficient (SHGC): This rating tells you how much solar energy the window lets through. The lower the SHGC, the less solar energy transmitted into your home. Windows can fall anywhere from 0 to 1 on this scale, but typically fall into the 0.25-0.8 range.
  • Visible Tranmission (VT): This window glass rating is pretty straightforward; it measures the light you can see coming through the window. The higher the rating, the more light that is let through. Another, 0-to-1 rating, the VT of most windows is between 0.2 and 0.8.
  • Air Leakage: Face it, your home isn't air tight. This rating measures, in cubic feet, the amount of air per minute passing through one square foot of window area. Lower AL ratings equal less air sneaking out and greater efficiency. Most building codes require require an AL of no more than 0.3 cfm/ft2.
  • Condensation Resistance: This one is important for people who live in damper parts of the country. It measures how well your window resists water build-up. The higher the condensation resistance rating--measured on a scale from 1 to 100--the less condensation build-up the window allows.

These window glass ratings are important for anyone looking to buy new windows. Be sure to shop around for the best deals, but keep in mind that if you meet certain standards set by Energy Star, you could qualify for a $,1500 tax break.

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