I tried spray foam insulation in my attic and it's way overrated

Everyone online swears by the stuff, but after sealing up my 1920s bungalow in St. Paul last fall, I ended up with moisture trapped behind the foam and a mold problem that cost me $400 to fix. Has anyone else had better luck with rigid foam boards instead?

2 comments

2 Comments

lisa_ross161mo ago

Yeah that's rough lol but I gotta say something here - the problem isn't spray foam itself, it's that it was applied wrong in a 1920s house. Older homes like that need to breathe, and sealing them up tight with closed cell spray foam without proper ventilation planning is asking for trouble. Rigid foam boards are definitely better for that kind of home since you can install them with an air gap behind them, which lets moisture escape. You probably would've been fine if you used open cell spray foam instead of closed cell too, since open cell is way more vapor permeable and less likely to trap moisture against those old wood walls. Either way, that $400 fix sucks and I feel your pain lol

michaelw261mo ago

Man $400 is still a lot though, I paid $600 last year to have a guy rip out half a wall of the stuff that was foamed directly onto knob and tube wiring. That was a fun surprise when I went to change a light fixture and found the wires literally cooking inside the foam. The old knob and tube guys really knew what they were doing leaving an air gap around everything, and spray foam just ignores all that ancient wisdom.