Hello all, I live in zone 5a in a 100+ year old house. I’d like to insulate my rim joists (rigid foam with a spray foam perimeter) and I’m curious how to approach it given the circumstances. I have a block foundation which the rim joists rest on directly – there is no sill plate. On three of the walls, the rim joists rest a few inches inward on the block, which often exposes the block’s cavities. On the south end of the basement, the rim joist sits about two feet above grade. On the north end, it sits at least eight feet above grade (my house is built on a steep hill, sloping down as you go south to north). I’m curious how I should handle the exposure of these cavities.

With two inches of rigid foam plus however much spray foam, I imagine these cavities will be covered up. Will that create a an environment that could lead to moisture concerns? Should the masonry cavities be filled? I’ve learned that perlite appears to be an option, but I know little about how recommended it is.