Sealing 101
How to Air Seal New or Replacement Windows with Polyurethane Foam
by Doug Caffoe
Doug@Fomo.com

Energy efficiency is a topic on the mind of every contractor and homeowner, and air sealing new or replacement windows is one of the easiest ways to increase the efficiency of a home or building. Most homeowners are concerned about the energy efficiency of the new windows being installed, but they often don’t realize the additional energy savings that can be achieved by air sealing around their windows—something that can’t be done with traditional insulation methods. The gap between the window and the framing can be the biggest culprit when it comes to air leakage. Plus, it’s relatively simple to install and it offers window installers a way to bring even more value to their customers.

Creating an air tight seal on windows is a simple, four-step process when using a door and window sealant. Most polyurethane foams can be used with a straw applicator or professional dispensing unit for increased control and metering.

Before using any polyurethane foam product, be sure to follow the proper personal protective equipment industry guidelines. One-component polyurethane foam products should be used in well ventilated areas with safety glasses or goggles, nitrile gloves and clothing that protects from skin exposure.

Step 1:
Use masking tape to protect the vinyl of the window in the event the cavity is overfilled. Note that uncured foam can also be removed with a product such as a solvent or acetone.

Step 2:
Select a low-pressure build, closed-cell foam that won’t bow windows, particularly vinyl replacement windows. Make sure the product is warm (between 65-80 degrees). Apply the dispensing unit or straw. Shake the can and then fill the gap between the window and the frame one-third full of foam, and be careful not to over fill.

Step 3:
Wait for the foam to expand—the expansion should fill the gap. Let the foam cure for one hour and do not cover the foam until it has fully cured and expanded. Cure times can differ from product to product, so you should always check the product label for accurate cure information.

Step 4:
Once the foam has completed its expansion, apply the moulding to the frame of the window. It is important to wait until the foam has fully expanded to allow the foam to fully cure from the ambient humidity. Enclosing the foam too early will not allow it to fully cure. If the foam expands beyond the cavity, use a utility knife to cut off the excess foam.

Note: When replacing sash-weight windows, there may be extra gaps that need to be filled. In this instance, the recommendation is to use a two-component, low-pressure spray polyurethane foam (SPF) to insulate larger voids, rather than a one-component foam sealant which is best suited for a bead application. Please note there are different recommended safety guidelines for using a two-component low-pressure SPF.

Doug Caffoe is vice president, business and market development for Fomo Products, and is certified as a building analyst by the Building Performance Institute.

DWM
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