Rim joist insulation is often the best return on a small insulation project because the rim joist is a short band of framing that leaks a surprising amount of cold air into the basement. Spraying closed-cell foam into each joist bay seals the air leaks and insulates the wood in one step, and it avoids the condensation problems that fiberglass stuffed in those bays often causes. For most Iowa homes with an unfinished basement, it's a one-day job or less. If your basement feels