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The Architectural Products Company

Window Air Infiltration

Getting an ideal window for your Columbus, Ohio home is all about finding an ideal balance of aesthetics and function. To find this a homeowner must navigate design and material options, and figure out what vital factors contribute to making an energy-efficient window. But you needn’t try to handle it all on your own. At APCO our team specializes in offering superior, top-class windows, and we want to help you understand what makes a great window great.

One of the five major factors that contributes to a window’s efficiency is air infiltration, and for now we would like to focus on that. How does infiltration impact efficiency, and what are you looking for in an infiltration resistant window? Follow along while we detail the basics.

Outside air infiltrating to
the inside of your home.

What Is Air Infiltration?

In essence a window’s air infiltration score details how much air leakage occurs at the joints in the frame. Much of what impacts heat gain and loss in a home is attributed to this, and thus the rating plays an absolutely huge role in what constitutes an efficient window.

The air infiltration rating is expressed by a numerical value that shows the amount of air infiltration by cubic feet. It looks something like this: cfm/sqft=rating, or cubic feet per minute compared by square footage of the window equals rating. To keep this simple we’ll go with what ENERGY STAR® constitutes as a window that is acceptably infiltration resistant, which is a window that offers AL (Air Leakage) ratings of .30 or lower.

With an AL rating, the lower the number the better, with .20 being a more leak-resistant window than a .30 window, and so on. Absolute top-end windows can feature ratings as low as .10, but this is not only uncommon, but often less worth it than it might seem. The optimal option is finding the window that is the correct size for your needs that offers respectable ratings at a cost you can be happy with!

Be Cautious of Window Size

It’s very, very worth noting that the size of a window does factor into its air infiltration rating. Since the measurement of the window factors into the formula, a smaller window will almost always have a lower AL rating than a window of the same materials and level of quality. This can be very misleading when buying windows, and a few less scrupulous window manufacturers occasionally use this confusion to their advantage when selling.

What Impacts Window Air Leakage and Ratings?

There are a few important factors to consider when looking for a low leakage window, including:

  • Window design. The actual window style can impact infiltration, as in a double pane window might have a lower rating than say a single pane, or vice versa. Crank style windows typically have some of the lowest (see: best) ratings aside from fixed windows, for example.
  • Weatherization. Weather stripping provides a direct reduction of air leakage, making it a highly desirable trait in new window installation.
  • Weep holes or no weep holes. Weep holes are essentially a work around for water intrusion, but a good window is effectively sealed against water and thus doesn’t need these potentially very leaky features.


“My new windows and patio door are beautiful. The service from showroom to installed product was excellent. I also feel, through shopping comparisons that I received good value for my investment.” – Susan from Columbus

APCO is driven to bring you the best window products and the best window installation service possible. We offer the best window products and high quality window installation services throughout the following cities and their surrounding areas: Bexley, Columbus, Dublin, Gahanna, Grove City, Lewis Center, Pickerington, Powell, Reynoldsburg, Upper Arlington, and Westerville.

For a quote or to schedule service for the best window installation in the Columbus area, contact us today »

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