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Why the Air Leakage Window Rating Is Important

When buying replacement windows, you might want to check the energy efficiency ratings, such as the u-factor or solar heat gain coefficient (SHGC). These ratings measure the window’s ability to insulate and regulate heat loss. However, many homeowners tend to forget about the air leakage window rating. Understanding this rating and using it to help determine the best replacement window is important for your home and energy savings. 

 Air Leakage Window

What Is Air Leakage?

Air leakage is the measurement of air that passes through the window assembly itself. It’s a common misconception that replacement windows create a vacuum and do not allow air to pass through them. However, windows have many parts, and air can sneak through anything. 

The National Fenestration Ratings Council® (NFRC) determines the air leakage rating. When looking at air leakage, you should see ratings between 0.1 to 0.3. Windows that have the lowest number possible allow the least amount of air infiltration. For instance, a casement window with an air leakage rating below 0.3 means less air can pass through it. To ensure that the number remains as is, you should have your windows installed by a professional window company to make sure there are no drafts. 

Why Does Air Leakage Matter?

The amount of air that passes through a window is an important rating. Unfortunately, air leakage isn’t a required window rating. There are even companies that completely leave it out of the discussion, focusing only on NFRC Performance Ratings. In cases like this, it might mean these windows are lacking in other areas, so be sure to take caution. 

Additionally, air leakage ratings below 0.1 are not recognized by the NFRC. This is because there is no significant difference between one window and another when the numbers are that low. Still, it’s wise to know more about your windows before making such a huge investment in your home. As long as the window has an air leakage rating below 0.3, it is recognized as an energy-efficient window by the NFRC and Energy Star.

If you’re searching online for high-quality replacement windows, look no further than Renewal by Andersen® of Wyoming. We offer a wide variety of window options, from picture to sliding windows. Call us today at (307) 472-2199, or fill out our contact form to set an appointment. We proudly serve homeowners in Douglas, Gillette, Cheyenne and surrounding areas.


"We are very pleased with our new windows and sliding door. The crew showed up when they were scheduled and had to work through snow drifts. They all were very professional, efficient and respectful. They made sure we were knowledgeable about how to use the windows and had us inspect everything before they were done. Great job!!"

Antonio & Peggy Escamilla
Apr 11, 2019

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