I'm converting a carport into heated space and decided to install a subfloor to raise the room to the same level as the rest of the house. I have roughly 1"-3" of clearance below my floor joists, so it isn't a crawlspace. I'm not planning on making it a vented space, and I've read about different approaches to seal spaces like this for insulation purposes.
Here is a picture of the most difficult part of the insulation project before the rim joist is installed:
I'm trying to figure out which insulation solution is the best for my scenario:
- It's technically an 'unvented crawlspace'. Can I use air-sealed rigid foam insulation along the rim and above the bricks and be done with it?
- Should I use R19 kraft-backed batts all the way along?
- Should I use R30 kraft-backed batts all the way along?
- Combination of two of the above?
Note: I'm in US climate zone 3 and care more about cooling my house than heating it.
I've read about heat soaking through the floor. Would this be an issue with approach #1? Would the difference between R19 / R30 actually be noticeable?
Best Answer
On a similar project, I put down 2" (?) foam board insulating panels, then filled the rest of the cavity with Rockwool bats. Inspector was happy. Here's what it looked like from the outside, before the wall was finished (opening used to be a doorway)
Edit 1: Added picture of filled joist spaces
No, I filled the entire cavity
EDIT 2
Original plan called for (from the existing slab upwards) crushed stone, 6 mil vapor barrier, 4" concrete slab, up to near the top of the foundation wall. Then the sill plate with the floor joists on top of that. Final step was filling the rest of the void with closed cell foam insulation. We deviated a bit because of the added cost of the stone & concrete.