Open or Closed Cell Spray Foam for Rim Joist and Garage Ceiling
I’ve got a raised ranch house in S. Ohio, the LR is over the garage. Walls are brick veneer.
1) Basement: I’m finishing the cement block basement now. The interior of the walls will be 2″ EPS with 2x4s laid flat and TAPCONed to the concrete block, then mold-resitant drywall screwed to the 2x4s. Right now I’ve got access to the rim joist and want to insulate it with spray foam (to cut air infiltration and also to increase R-value). I definitely don’t want moisture problems, and am thinking open-cell foam might be a better answer than closed cell for this reason, despite the lower R-value per inch. Thoughts?
2) Garage ceiling: The floor of the living room is over the garage and gets very cold. Right now we have no insulation between the two–just a plank sublooor, rosin paper, and oak hardwood floor. Once the garage is actually used to hold our cars (my dream) I know we’ll be frequently moving wet/snowy vehicles in and out. My budget certainly won’t alow 7″ of spray foam, but I was planning on at least an inch of spray foam on the subloor to reduce air infiltration and introduction of fumes from garage to the living areas . Some heat leakage to the garage is actually desirable–it keeps the vehicles and my pipes from freezing up. I’ll be adding some insulation to the interior of the exterior garage walls later, even though it’s not actively heated.
Questions/comments: Open cell or closed cell spray foam? I’m a fan of letting trapped moisture get out, but the wet vehicles and resulatnt water vaopr load in the garage adds another twist. Also, should I add Type X gypsum board to reduce risk of flame spread through the garage ceiling, or is fire-resistant spray foam enough? I’m going to miss the ability to store supplies, etc between the garage ceiling joists.
Thanks for any thoughts/suggestions
Replies
Open or Closed Foam for Rim Joist
Did you ever get an answer to your question? I'm getting ready to do the same project, and I'm going with open celled foam because I get a lot of condensation and think it will dry more readily, but I'd like to know what a professional thinks. Or at least a fellow non-professional.
Wow, I have no idea of why this question wasn't answered originally.
Don't do the open celled, unless you want water vapor to dry into your living space.
Building Science did a take on how to do crawl spaces, which this basicly is. Their take was to attach rigid foam board to the underside of the joists, then for garage you would drywall over that. You could insulate the joist bays as well, depending on your insulation needs.
You want to keep the cold wet air out of your house, and out of your insulation!