We’re (finally!) about to proceed with our basement finishing project.

I’m planning on covering most of the wall (minus the bottom foot or so) with foam board, taping the seams, and sealing the tops and bottoms with spray foam, then framing with 1 5/8 metal furring studs.

I’m planning on using the pink extruded foam. Probably 1.5″ (r7.5). Should I also consider the expanded foam? It’s, of course, cheaper, but I’m thinking that may have more potential to hold water if water ever came in contact with it (+ the humid summers).

A few other insulation-related questions:

– should all of the spaces between floor joists near the exterior wall be insulated? (I’m thinking ‘yes’). The exterior of the house at that level is brick and no insulation (other than that insulating board they used 70 years ago)…if that matters. We’re probably going to keep the floor joists above open, however, so I’ll have to figure out how to camoflauge the pink.

– does it make sense to seal the tops and bottoms of the panels with spray foam? The walls in some parts aren’t flat (as they were coated with a VERY rough plaster finish) so there’d be an air gap there if I didn’t seal. My understanding that the air gap is a potential problem if moist summer air can get back there and condense.

– should the entire permimeter foundation wall be insulated or just the finished area (or does it matter)? I was going to enclose the furnace/tool room and the laundry area, but not formally finish them. I’d then insulate the partition walls instead. The only reason to insulate the entire permieter that I could think of would be to keep the floor above a little warmer in the winter. But a rug could take care of that too ;o) (Though, I’m now leaning towards insultating the entire perimeter, though not necessarily heating the whole thing)