Update: changed my mind about spray foam insulation after a mold surprise

I had my whole attic sprayed with closed cell foam back in March and thought it was the best thing ever. But last week when I went up there to run some new wiring, I found a spot where water was trapped between the foam and the roof deck. Turns out the crew didn't seal a small gap near the ridge vent and moisture was getting in. I had to cut out a 3x3 foot section of foam to let things dry out and then patch it with a different insulation type. I'm starting to think that with my old house's weird roof angles, I should have gone with a vented system instead. Has anyone else dealt with moisture getting trapped behind spray foam in an older home?

3 comments

3 Comments

jana1192mo ago

That 3x3 spot sounds more like a bad install issue than a systemic problem with spray foam honestly...

wilson.kelly2mo ago

Did you ever have that one contractor who used spray foam and then disappeared for two weeks because he said his truck broke down in another state? lol. I had a guy spray a crawlspace and he left the cans sitting out in the sun, ended up with this sticky mess that looked like a giant melted marshmallow had a fight with a hairdryer. Took me forever to chip it off the foundation. Point being, sometimes people just screw up the basics no matter what product they're using.

the_parker1mo ago

Watch the gap between the foam and the wood framing too, because @wilson.kelly already nailed it about installers skipping little things that snowball. That 3x3 spot could be from the foam not sticking right if the surface had dust or moisture on it, even if the rest of the job looked fine at first. It's like painting a wall without cleaning it first, you'll get some spots that peel later no matter how good the paint is.

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