From special coatings on the glass to sturdy frame materials, quite a few factors go into making a window truly energy-efficient. However, you should consider another factor when installing new replacement windows: how much air they allow to leak in or out.

No window can block all the air from indoors to outdoors or vice versa. The better the window’s air infiltration rating (or air leakage rating), the less you’ll have to deal with drafts and losing climate-controlled air. Let’s look closer at the air leakage rating and why it’s important for you.

What Window AL Means

Window air leakage, commonly abbreviated as window AL, refers to the amount of air that makes its way through your window. The lower the number, the less air can escape through the window, and the more insulated your home will be. While you’ll never see an AL value of zero, a well-made window should have a very low number.

Unlike many quality ratings, window air leakage is not generally a required value to display. Most trustworthy dealers will still tell you, however. Any place that tries to hide its windows’ AL rating likely has poor-quality windows.

Recognizing a Good Window Air Leakage Rating

Energy Star-certified windows are required to have an AL value of 0.3 or lower. This means that less than a third of a cubic foot of air can make it through the window every minute. Not every window will display this value on the NFRC label since it may have achieved the rating through a different method. However, if you see that a window is Energy Star-certified, rest assured that it has an excellent AL number.

Finding Reliable Replacement Windows

A truly energy-efficient window relies on several different design choices. This efficiency keeps your home at a comfortable temperature and reduces your energy bill. As you shop for replacement windows, don’t forget to check the AL rating. The better the rating, the better the window will be for your home.

Contact us to learn more about our window models and their air leakage levels.