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Understanding the Numbers in an NFRC Label

The National Fenestration Rating Council (NFRC) uses certain specific standards to measure the quality and performance of replacement window products. Contractors use these ratings to find the right window solutions for their clients. While some of these numbers can be a bit technical, it still pays to understand what they mean. Familiarizing yourself with these performance standards means you’ll be making more informed decisions the next time you shop around for a window replacement.

Understanding the Numbers in an NFRC Label

The NFRC Label

All new replacement windows carry an NFRC label that shows their ratings on two extremely useful energy efficiency performance criteria. These are the U-Factor and Solar Heat Gain Coefficient (SHGC). Two additional standards are also displayed, and they provide extra information about the product’s overall quality. These include its Visible Transmittance (VT) and Air Leakage (AL).

U-Factor and SHGC

U-Factors measure a window’s ability to insulate your home. The lower this number is, the better it is at resisting the heat from the sun. On the other hand, SHGC is a measure of how much heat it allows to pass through itself. Lower SHGC numbers mean your window is better at keeping your interiors cool even under direct sunlight.

VT and AL

VT deals with light. Higher VT ratings mean you’re getting more light for your room, negating the need for indoor electric lighting during daylight hours. AL measures air transmission more commonly known as “drafts.” This means you want to look for low AL ratings to reduce the number of drafts you get in your home.

Learn more about window performance standards from our professionals at Renewal By Andersen® of San Francisco, your number one local window replacement company. Give us a call at (510) 263-3210, or fill out our online contact form to schedule a no-obligation in-home consultation and request a free estimate today. We serve homeowners in San Francisco and all nearby areas.


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