We are converting our garage to living space. We plan on sealing the concrete with a polyurethane sealer, using pressure treated sleepers as floor joists, covering this with 3/4" plywood subfloor, and then installing hardwood flooring. We want to maximize the floor insulation. The floor slopes so that the sleepers will be about six inches near the outside wall and only about two inches on the inside wall. We would like a recommendation on the best type of insulation (ie closed cell polyurethane sheets, spray in closed cell foam, etc). We are also curious if we should leave an air gap either above or below the insulation to allow for circulation. Any help would be appreciated.