I have a home built in 1999 with an unfinished basement. It has a 7' tall poured concrete foundation walls and 2 rows of concrete block on top of that (9' high total).
It is a walk out basement, so the walls are very cold - especially where the wind is blowing on them. The concrete blocks (the few I can somewhat feel inside) are unfilled. I feel a cold breeze coming in on top of these blocks. Also, the 2x10 rim joists are insulated with unfaced fiberglass insulation, which still lets some cool breezes in. The home is brick.
I was planning to insulate the walls with 2" thick XPS foam, but have some questions about installing this, as well as insulating the rim joists better and cavities in the top of the block.
The stud walls, or furring strips (haven't decided), would go on top of the 2" insulation.
1) What is the best way to seal between sheets of the foam (can't find 2" XPS tongue and groove locally)?
2) What is the best way to insulate the rim joists and block? I was thinking spray foam, but not sure if there are more effective ways. I expect energy costs to escalate quickly, so I'm willing to spend a little more for better performance. I live in SE Michigan.
3) Do I still need a double top plate since the basement walls will be all non load-bearing?