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How to Read the NFRC Label on Windows and Doors

Have you ever tried to make sense of the energy labels on exterior products? It can feel a bit like a foreign language. The two main ratings include the U-Factor and the Solar Heat Gain Coefficient (SHGC). These energy ratings give a reference point to the overall performance of windows and doors. However, these are not the only two measurements listed on the label. Seeing all the numbers can be confusing, especially if you don’t have any experience. What do they all mean? Here is what you need to know about reading the energy labels and finding the best windows and doors in Phoenix, AZ.

What is the NFRC Label?

The National Fenestration Rating Council released this rating system in 1994 with the mission to provide fair and accurate ratings for all exterior products. To be labeled as Energy Star, windows and doors must meet a specific set of standards under the NRFC ratings. This way, homeowners can find the most energy efficient exterior products for their region. Here is what each measurement means:


This first rating on the NFRC label references how efficiently the window prevents non-solar heat. The ratings range from .20 to 1.20. The lower U-factor rating signifies that the window has a great ability to reduce heat transfer, and keeps the inside from heating up like an oven. You can imagine, in Phoenix, AZ you want low U-Factor ratings because these windows provide significant amounts of insulation.

Solar Heat Gain Coefficient (SHGC)

This rating is similar to the U-Factor, but the difference is in solar radiation. With solar heat gain, you will find that during different parts of the day, certain rooms will warm up. The rating ranges from 0 to 1, and again, a low SHGC is most energy efficient. These windows and doors prevent large amounts of solar radiation from entering the home.

Visible Transmittance

If you like a lot of natural sunlight entering your home, this is the rating you want to pay attention to. This measurement indicates how much sunlight passes through the glass without obstructions. The values vary between 0 and 1, and window panes usually fall between 0.3 and 0.7. Higher numbers have more visible light and tinted windows have lower VT ratings.

Air Leakage

This measurement is in cubic feet per square foot and indicates the amount of air lost or gained in the cracks of your window assembly. Usually, the measurement falls between 0.1 and 0.3, because no window or door is completely leak proof. But the lower the number, the less air that gets through. These products are less prone to drafts and condensation. However, this rating is not required and many manufacturers choose not to post it on the labels.

Condensation Resistance (CR)

This is another optional rating that measures the window’s ability to resist condensation formation on interior surfaces. The measurement ranges between 0 and 100 and here, the higher ratings have better condensation resistance.

Call Freelite for Help Reading NFRC Labels

Still not ready to tackle energy labels on your own? The good news is, you don’t have to. Our experts offer you a no-hassle, no-pressure way to purchase windows and doors Phoenix, AZ. With over 30 years in the business, we can make sure you get all your questions answered and feel confident in your product choices. If you are looking for new windows and doors call (602) 233-1981 or stop by 331 W. McDowell Rd., Phoenix, AZ 85003.