I'm in the process of buying a house, and I was planning to insulate the rim joist by applying a 1 to 2 inch layer of spray foam and then filling the rest with fiberglass insulation. However, someone advised me against this method. Can anyone explain why that might be a concern?
3 Answers
I don't think there's any major issue with it! The only downside is that it can make future home improvements like running new wires or plumbing a bit trickier since you'd have to cut through the foam to access it. Personally, I don't mind making those cuts, especially for the few times I need to pull new lines—just patch up the foam afterward! But hey, just my two cents. You might want to consider how often you might need to access that area before deciding.
Many people recommend against using certain types of spray foam insulation for rim joists. The consensus seems to be that if you're doing this project, using rigid foam boards is a better option; you can still seal it with spray foam after placing those. This approach seems to balance both insulation and moisture concerns.
It's definitely a common concern about sealing the rim joist with foam. Some folks worry it might trap moisture against the wood, which isn't ideal. But many professionals suggest using rigid foam boards for a more cost-effective solution and then sealing the edges with spray foam. After that, filling in with fiberglass should work well. Just keep in mind that access for running wires and pipes will be harder once it's all sealed up.
Yeah, I've dealt with that before too! It's a hassle, but manageable if you're okay with a bit of extra work.