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A Window Shopping Guide: What NFRC Ratings Mean

Don’t underestimate how much unwanted outdoor heat enters your home through inefficient windows. According to the Department of Energy, heat gain and heat loss through windows can account for up to 25% to 30% of residential heating and cooling costs. That’s why it makes both practical and financial sense to install energy-efficient replacement windows.


How can you tell if a window is energy-efficient? By looking for the ENERGY STAR® label—only windows that have met the government-run program’s stringent performance standards have this label. Underneath the label are the window’s National Fenestration Rating Council (NFRC) ratings, which tell you which windows are suited to your area’s climate.


Here’s a quick overview of the NFRC ratings:

NFRC Ratings

  • U-factor – The U-factor indicates the window’s insulative capabilities. The higher a window’s U-factor, the better it is at preventing heat transfer.

  • Solar Heat Gain Coefficient (SHGC) – The SHGC gives you an idea of how much heat from the sun can pass through a window. The lower a window’s SHGC, the less heat can pass through the window glass.

  • Visible transmittance – A window’s visible transmittance indicates how much sunlight can pass through the window glass. The higher the visible transmittance rating, the more natural lighting a window can provide.

  • Air leakage – This rating gives homeowners an idea of how much air can enter their homes through windows. The lower the air leakage rating, the less drafty the window will be.

Assessing Energy-Efficient Features

When choosing an energy-efficient window, it’s important to look at the window’s overall performance rather than focusing too much on individual features. However, this doesn’t mean features provide no value. On the contrary, they can help maximize your returns on investment. For instance, Fibrex®, an exclusive wood-and-vinyl composite, has excellent insulative capabilities and resistance against abrupt temperature changes, helping lower your heating and cooling costs and protecting your home against extreme temperatures. For more tips on how to make the most of an energy-efficient window replacement, consult your local window contractor.


Want to learn more about our energy-efficient windows? Renewal by Andersen® of Dallas and Fort Worth offers a wide variety of premium windows as well as professional window installation services. To schedule a free consultation, call us at (972) 301-8660 or fill out this form. We serve homeowners in Dallas, TX, as well as the surrounding communities.