Fraud Blocker All About the Air Leakage Rating of Replacement Windows
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All About the Air Leakage Rating of Replacement Windows

One of the important things you need to consider when choosing double-hung or sliding windows for your home improvement project is the units’ energy performance ratings. The U-factor and the solar heat gain coefficient (SGHS) are the most common, both of which indicate the windows’ ability to insulate and regulate heat loss.

Window condensation

However, that’s not the only rating you need to look for when making your window selections. Read on to learn more about the air leakage rating and why it matters.

About Air Leakage

Air leakage is the measurement of air passing through the window assembly itself. The rating is usually determined before the unit is installed, so to make sure it stays the same, you must hire a reputable window company for your window replacement project.

This energy performance rating is measured on a scale of 0.1 to 0.3, with 0.1 indicating the least amount of air passing through the window. The number is determined by calculating the amount of air that can pass through a window in cubic feet per minute. It is then divided by the window’s total area. Another thing to remember is that the rating is based on a constant wind speed of 25 miles per hour.

The Importance of the Air Leakage Rating

The air leakage rating isn’t always shown in replacement window labels coming from the National Fenestration Rating Council (NFRC). However, if you are investing in ENERGY STAR®-rated windows, there’s a good chance that it will be indicated alongside U-factor and SHGC ratings.

Keep in mind, however, that air leakage is a tricky window rating that can get misinterpreted depending on which window contractor you talk to. Make sure you don’t overlook this particular aspect of the window replacement;  work with professionals who have the knowledge and expertise to guide you through this home improvement project and ensure you get the most out of your new windows.

Renewal by Andersen® of Montana offers the best selection of replacement windows in the area, including sliding windows and picture windows. Learn more about your options by calling (406) 812-8167 or filling out our contact form for a virtual consultation.


"I highly recommend Renewal by Andersen. We were treated well and everything went smoothly from start to finish. The company kept in contact with me before, during, and after the installation and let me know what to expect. I'm in love with my new windows! I will be using this company again when we refinish our basement. "

July, 21

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