I'm taking advantage of a rebate offer provided by my local utility company that allows me to insulate my drafty old house at a reduced rate. The auditor who analyzed our house listed, as part of his recommendations, that we spray foam in the basement. This would include the rim joists and three feet down the cement block walls. I'm new to this stuff and while I want maximum efficiency I worry that the spray foam may hide any issues I may be having with the sills or other areas the foam is covering. I'd love some opinion on this. I'd also love to know if in fact insulating in the basement (we'll be insulating elsewhere, too) is indeed worth doing in an older house (c. 1915) like mine. Thanks for any advice.