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How Do You Measure a Window’s Performance?

Are you upgrading to more efficient windows and sliding doors? To make sure you’re getting the best quality products, you need to check their performance through their NFRC ratings and ENERGY STAR® certifications. But what are the NFRC ratings and how does it help you find the right window for your home? Renewal by Andersen of Kansas City shares their insight:

How Do You Measure a Window’s Performance?


Two organizations take care of establishing the ratings of the products and testing them out. First, the NFRC (National Fenestration Rating Council) establishes objective energy-efficiency ratings for windows, doors and skylights, which are also known as fenestration. The NFRC is an independent non-profit organization that helps consumers compare products and make informed purchases through its established ratings.

While NFRC-rated windows, French doors, and other related products have a label affixed to them that displays their ratings, the NFRC are not the ones who test their performance. That part is handled by ENERGY STAR, which is under the U.S. Environmental Protection Agency. So, if an NFRC-rated product also has the ENERGY STAR certification, that means they’ve gone through additional testing!

NFRC Ratings

  • Visible Transmittance – This refers to how much light can pass through a given window. It’s usually found on the middle, bottom, or left side of an NFRC label.

  • Solar Heat Gain Coefficient (SHGC) – This shows the fraction of incident solar radiation transmitted and absorbed by a window. This is the top-right number on all NFRC labels.

  • Air Leakage – This lets you know how much air passes through its joints, and can be found on the middle, bottom or right side of an NFRC label.

  • U-Factor – This metric lets you know the rate of heat transfer and tells you how well the window insulates. It’s the top-left number on all NFRC labels.

  • Condensation Resistance – This indicates how well a product resists moisture build-up and can be found on the bottom row of the NFRC label on the left side.

If you’re searching online for “windows and doors installation”, be sure to check out the excellent services offered at Renewal by Andersen of Kansas City! Call us at (913) 385-1300 or fill out our convenient contact form online to request a free estimate. We serve Olathe and nearby areas.

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