James writes from Tuscaloosa, Alabama: "If I live in the South and have a vented crawl space. Should I insulate my floor or will that stop the house from cooling off at night?"

Answer: You can insulate the floor. Make sure you check with your local building code regarding the vapor retarder. High humidity regions can differ on the use and placement of a vapor retarder.

Click here for general instructions on the Owens Corning Web site for insulating crawl spaces under floors.