How to Air Seal New or Replacement Windows
with Polyurethane Foam
by Doug Caffoe
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
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.
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.
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.
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.
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
© Copyright 2012 Key Communications Inc. All rights reserved.
No reproduction of any type without expressed written permission.