3 Ways to Air-Seal Andersen® Windows

A window installation video walks through three ways to seal the gap between a window frame and the rough opening in the wall, the step that keeps outside air from leaking in around new windows and doors. A custom builder in Utah demonstrates the methods on Andersen windows, but the same choices apply to most window installations.

The first method is low-expansion spray foam, which she calls the cheapest and quickest option, though it can get messy on larger gaps and may not seal quite as tightly as the alternatives. The second is a backer rod (a foam cord pressed into the gap) paired with caulk, which costs more since it requires two materials but gives a more consistent seal, especially once the caulk joint between the window and the framing is smoothed out. The third is a specialized tape applied to the window frame, either before or after the window is set in place. It takes about as long to install as the backer-rod-and-caulk method but costs the most of the three.

None of the three is presented as better than the others; the choice comes down to budget and what feels manageable to install carefully. If you are having windows replaced or installed, this is the kind of detail worth asking your installer about, since a sloppy air seal can undercut the comfort and efficiency gains a new window is supposed to deliver, regardless of the window's own energy rating.