Window Energy Video

Find the Most Energy Efficient Windows for Your Home

This video explains window ratings and how to increase energy savings--using energy-efficient replacement windows is a good place to start.

Double- and Triple-Pane Replacement Windows: How They Work

Today's replacement windows are usually double- or triple-pane windows. This means they have two or three sheets of glass between the home and the outdoors, instead of one. Manufacturers usually fill the space between the glass with air, which increases the window's efficiency. Some manufacturers fill the space with argon or krypton gas, restricting the movement of hot or cold air.

Triple-pane windows are more energy-efficient than double-pane windows. Between the second and third pane, some manufacturers leave room for shades or blinds.

How Your Replacement Windows Measure Up

The National Fenestration Rating Council rates windows for energy efficiency using a U-value and a solar heat coefficient number.


  • Measures a window's energy efficiency
  • Values range from .25 to .50
  • The closer the number to 0, the more energy efficient the window

Solar Heat Gain Coefficient Number:

  • Measures how well a product blocks the sun
  • The closer to 0, the more the product blocks the sun
  • A high number retains more heat

Find these numbers on a label located on the window. Remember to consult your contractor with questions or concerns about energy efficiency and your replacement windows.

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