Ten Things to Know about Dual Pane Windows

December 15, 2009

The windows on your home are all areas of potential money loss to you--if they don't efficiently keep the outside air out, you end up running your heater or air conditioner more often and your energy bills go up. If you are thinking of replacing windows here are ten things you should know:

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  1. You can get an federal energy tax credit up to $1,500 for replacing windows. You can use this credit when you purchase approved dual pane windows that save energy. Products must be purchased between January 1, 2009 and December 31, 2010. Your credit is calculated on 30 percent of the purchase price of the approved windows and does not include the cost of installation. For more information specific to windows see the U.S. Department of Energy's Summary of Tax Credits for Consumers.
  2. Your utility company might offer a rebate or some other form of incentive for purchasing energy efficient dual pane windows. The quickest way to find deals is to use a search by state feature at the U.S. Department of Energy's Energy Star Rebate Finder tool.
  3. Not all dual pane windows are equally efficient. Efficiency depends on three factors: materials, construction and the environment in which the dual pane windows exist.
  4. Dual pane windows with inert gas between the panes are more efficient than windows with gaskets, and windows with gaskets are more efficient than windows with aluminum spacers.
  5. Dual pane windows with vinyl frames are more efficient than windows with wood frames, and windows with wood frames are more efficient than those with aluminum frames.
  6. An independent testing service, the National Fenestration Rating Council (NFRC), measures the efficiency of windows based on five criteria: U-Factor, Solar Heat Gain Coefficient (SHGC), Visible Transmittance, Air Leakage and Condensation Resistance. See the definitions and ranges of these window efficiency factors here.
  7. The U.S. Environmental Protection Agency rates dual pane windows for efficiency based on location and U-Factor and SHGC. See the Energy Star efficiency matrix for detailed information for your location.
  8. It is possible for windows to meet the Energy Star criteria but not carry the Energy Star label. This is due to the fact that some companies private label their windows from larger manufacturers whose windows are approved. However, it is your responsibility to be sure that windows for which you are claiming a tax credit meet the federal guidelines. That is one good reason why you need to know the definitions and acceptable values for approval (see point 6 above).
  9. Look for windows with weep holes. These small openings wick water away from the window and screen, prolonging the life of the dual pane window and preventing damage to the frame.
  10. If you see condensation between panes of your dual pane windows, that indicates a leak which means your window is not performing properly. Some higher end windows can be repaired, while lower quality windows will probably need to be replaced.

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