Hello, We are in the process of remodeling our 1930s house. I am planning on tearing out some sheetrock and firring (or is it furring) the studs in about 3 inches, they are only about 2.5 inches right now. Yes you heard that right, 2.5 inches on an exterior wall. Not a lot of insulation. Anyway, once I tear the sheetrock out and the blown-in insulation, should I prep the wall before I insulate? They used 1x boards back when they built this house. I have seen people prep for insulating by spraying expandable foam in all of the cracks. Any advice?