Understanding Energy Performance Ratings for Replacement Windows

Understanding Energy Performance Ratings for Replacement WindowsWith so much focus on energy-efficient replacement windows nowadays, the National Fenestration Rating Council (NFRC) has designed an energy-performance label to help homeowners and contractors more easily choose windows that will meet their needs. Because climates in different regions of the United States vary so widely, looking at this NFRC label can help ensure that your new windows will perform as you would like them to in your climate. Below, we look at the most common ratings found on an NFRC label to help you better understand the overall performance of the windows you’re considering.

The four main ratings found on an NFRC label are: U-Factor, Solar Heat Gain Coefficient (SHGC), Visible Transmittance (VT), and Air Leakage (AL).

  • U-Factor – This rating measures heat loss, or how well a window will prevent interior heat from escaping a home. The U-Factor for a replacement window ranges from 0.20 to 1.20, with a lower score meaning the window is better at keeping heat inside.
  • Solar Heat Gain Coefficient – This rating measures heat gain, or how well a window will prevent exterior heat from entering a home. The SHGC ranges from zero to one, with a lower score meaning that less heat will be able to enter the home.
  • Visibility Transmittance – This rating measures how much daylight will be able to pass through a window’s glass and is contingent on factors such as Low-E coatings, tints, colored glass, etc. The VT measures between zero and one, with a higher score meaning that more natural light will be able to pass through your windows.
  • Air Leakage – This rating measures how much air will be able to enter a home through the window. The AL value ranges from 0.1 to 0.3, with a lower score meaning that your home is more airtight, and thus more energy efficient.

Ultimately, when it comes to analyzing the energy performance ratings of replacement windows, you should look for U-Factors, Solar Heat Gain Coefficients, and Air Leakage ratings that are lower, and Visibility Transmittance ratings that are higher.

To learn more about what to consider when purchasing replacement windows, click here to locate a Sunrise Windows dealer in your area.

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