Window Insulation | Two Methods for Insulating Windows & Doors

October 8, 2017

When you install your new energy efficient windows in your home, you need to pay close attention to the window insulation that fills the gap between the window frame and the wall studs. Leaving this gap unattended will all but eliminate the benefits associated with the installation of new insulated glass windows. The two methods for insulating windows and doors are filling the gap with spray foam, or Chinking, which is basically filling the gap with fiberglass insulation. Let’s take a quick look at both methods:

Installing Spray Foam Window Insulation

The easiest method of filling the air gap around your new windows is simply applying spray foam insulation. However, there is more to this process than you would think. For the best results, you need to apply the foam in 2 distinct layers. The first layer creates an air tight seal, while the second layer fills the remaining gap for maximum insulation value.

Spray the foam around the entire perimeter of the window or door, filling the void to about 75% of its depth. If your wall studs are 2×4’s you should spray about 3” of foam for the first layer. Allow the initial layer to fully cure, which should take about an hour or less. Then come back and apply another layer over top of the first to fully fill the void. This second layer will likely expand beyond the edge of the 2×4’s. You will need to come back and cut the excess off with an X-Acto knife once the spray foam is fully cured.

Use “Low Expansion Foam Sealant” to fill the gap. Otherwise the foam will expand too much and create a mess. Your mission is to fill the void without putting too much pressure on the window frame.

Installing Fiberglass Insulation Around Windows & Doors

If the gap is extra wide, the use of spray foam may be cost prohibitive. In this case you can fill the wider gap with pink fiberglass insulation. Rip the fiberglass to a thickness that is about double that of the width of the gap. So, if the gap around the window or door is 2” wide, you want to tear the insulation to a thickness of 4”. The width of the insulation should be roughly the same as the width of the studs. For 2×4 studs cut the insulation to a width of 4”. For 2×6 studs, cut the insulation to a width of 6”. Don’t cut the insulation too wide or too thick as this will actually reduce the R-Value of the insulation.

Use a flat putty knife or pry bar to push the insulation into the gap. Be careful to maintain the integrity of the insulation. Your goal is to maintain the overall width and thickness of the insulation to fully fill the void without bunching up the insulation. Wadding up the insulation will reduce its overall effectiveness as a thermal barrier.

Window Insulation Installation Video

The following video demonstrates two easy methods for installing window insulation. The first part of the video shows the spray foam insulation method. Part II of the video illustrates the best way to install pink fiberglass insulation to fill the gap between the window and the wall studs.


Window Insulation Quick Tips

If you happen to drop any of the spray foam on the wall or floor, resist the temptation to wipe it off while it is still wet. You will only make a further mess. Allow the foam to cure and it should easily come off the wall or floor in one piece using a plastic paint scraper.

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Do you have questions about how to install window insulation for your new windows? Contact our support team at (815)-634-8922.