What San Diego Homeowners Need to Know About Air Infiltration as it Pertains to Replacement Windows

Most of the San Diego homeowners we meet with want the most energy-efficient windows possible (or at least the most energy-efficient windows that are within their budget). Many replacement window companies focus mainly on a window’s U-Factor and Solar Heat Gain Coefficient ratings, both of which are very important in determining the energy efficiency of a window, but they fail to mention a window’s air infiltration rating.

What is Air Infiltration and Why Is it Important?

Air infiltration, sometimes called air leakage, refers to the amount of air that is allowed to pass through a window. Windows with good air infiltration ratings allow very little air to move either in or out of your home through your windows, while those with poor ratings let in hot air during the summer months and cold air during the winter months. Installing replacement windows with a poor air infiltration rating in your home will cause you to have to use more energy cooling or heating than you would if you installed windows with a good air infiltration rating.

As much as we’d love to sell our customers windows that are completely airtight, they just don’t exist. There is always a trace amount of air that will be able to travel through the small gaps between the window’s sash and frame. However, some windows are definitely better than others when it comes to air infiltration.

Windows made by Anlin, for example, have an excellent air infiltration rating (when it comes to this rating a lower number is better). To give you some perspective, a good rating, according to industry standards, is .30 cubic feet per minute at 25 milers per hour wind-load. Anlin has windows with an air infiltration rating as low as .01—making them up to 30 times better than the industry’s requirements when it comes to air leakage!

When you look at the air infiltration ratings on windows from various manufacturers, make sure you are comparing apples to apples. This is important because a fixed window—one that doesn’t open or close—will almost always have a better air infiltration rating than a window with a movable panel, such as a sliding or hung window. So, if you’re looking at the air infiltration number on a picture window by Anlin and want to compare it to windows by Simonton, make sure you look at what the rating is on Simonton’s picture windows as well.

How Does Anlin Make Their Windows So Resistant to Air Leakage?

The difference between a window with an excellent air infiltration rating and one with a not-so-good-to-average rating usually has to do with the window’s weatherstripping. Anlin’s windows have triple-fin weatherstrips. Windows by other manufacturers may only have a single fin and probably won’t have the amount of plush filler in their fins that you’ll find in Anlin’s windows. The triple-fin design in Anlin’s weatherstripping also helps give their replacement windows a watertight seal.

If you want to learn more about why Anlin’s replacement windows are some of the best on the market when it comes to air infiltration ratings, take a look at this video:

Window manufacturers don’t always publish their windows’ air infiltration ratings—it isn’t required that they do—so make sure you ask your replacement window dealer about this important rating. Remember, if the number is below .30, the window is considered energy efficient by ENERGY STAR. But the lower the number, the better.

Do you have questions about replacement windows? BM Windows can help! Schedule a free consultation with one of our knowledgeable team members, who can help you determine which windows are the best for your particular San Diego home.