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What Happen If Spray Foam Insulation Gets Wet?

When it comes to insulating your home, you are considering more than just heat in summer and cold in winter.  While temperature regulation definitely affects your energy bill, insulation is also meant to be a barrier against moisture. Moisture not only threatens the life and integrity of the wood, it can also lead to things like mold and mildew, which can threaten the health of your family.  You have likely rad about the greater energy efficiency of spray foam insulation, its superior seal, and the fact that it can actually strengthen your walls.  However, you may have questions about how spray foam reacts with moisture.  In other words, what happens if spray foam insulation gets wet?


There are some myths out there about spray foam and water that we’d like to clear up in this post by giving you some facts to answer this question.  First, what happens when the foam itself gets wet?  Will it still dry properly?  Open cell spray foam insulation will still dry completely after getting wet.  If the amount of water is extensive, the shape may be affected, but it will still dry completely, and then any shape imperfections can be filled in easily.  If spray foam polyurethane gets wet after a couple of minutes, it will still dry effectively with no shape problems because it forms a “skin” that is water resistant.  Single component foam is more affected than polyurethane but can still dry; it just may need some shape correction.  In addition, because spray foam is not a “food” for mold, there is little danger of mold becoming a problem even if it gets wet.  Closed cell foams also do not absorb water, which is very beneficial in flooding zones.  In fact, because it is water resistant, it is often used as an effective repair for leaky basements.


What about wet surfaces?  Can spray foam insulation be used on surfaces that get wet?  Will its water resistance trap water and cause mold or decay?  This is one of the myths about spray foam.  Spray foam has been used and installed in various places where water is a consideration, such as the underside of roof decks, for decades, and there is no record of it causing deterioration to the wood, even when the wood gets wet.  It seals any cracks or crevices and repels the water, protecting the wood more effectively.  In addition, in colder climates, it helps to keep the rook deck cold, thereby preventing ice damming. In warmer climates, potential customers have sometimes been concerned about humidity and vapor as potential water problems.  Actually, the composition of closed cell spray foam allows a controlled flow of moisture vapor as it separates the inside and outside temperatures, which controls condensation more effectively.  And even if wood is wet when spray foam insulation is applied, repeated tests indicate that while the lumber may dry more slowly, it will dry, and the seal will still be in effect.  So while it is best practice to spray the foam onto a dry surface, even a damp surface can still be protected.


In short, water does not have to be a concern with spray foam insulation, whether the issue is a spray foam that gets damp after installation or a spray foam that is installed on a portion of the home that may have some dampness.  If you still have questions about what happens if spray foam insulation gets wet, contact Airseal, and we’ll be happy to address all of your concerns and inquiries about spray foam insulation.