Hey everyone! I'm currently finishing my basement after dealing with some past water issues. We've tackled exterior waterproofing, but I have some concerns moving forward. I live in Canada, where winters are cold and summers can get hot. Here's what I'm planning to do: install foam board against the block foundation, frame with a 1" gap between the foam board and framing, and add batt insulation between the studs. My main questions are: 1. Is a poly vapor barrier necessary? 2. What's the best way to insulate and protect the rim joists from moisture? Thanks for any advice!
3 Answers
Check out this authoritative resource for more info on basement insulation: [BSD-103 Understanding Basements](https://buildingscience.com/documents/digests/bsd-103-understanding-basements)
I went ahead with 1.5-inch pink foam board glued to the concrete blocks, making sure everything was sealed well with foam. From my research, that setup actually acts as a sufficient vapor barrier on its own!
I wouldn't worry about a vapor barrier; the foam board should do the trick. I used 2-inch foam glued directly onto the blocks and framed right up against it. In a tight spot, I had to use foam with slots for 2x3 studs, which worked well. Just make sure to use suitable adhesive for foam, and don’t forget to tape the seams and spray foam the edges! For rim joists, cut some foam to fit snugly and spray foam around it. Oh, and consider extra insulation in the rim joist area since it can be a cold spot!
Thanks for the tip!