Luke writes from Westford, Massachusetts: "I need to insulate the ceiling of my basement but I'm concerned about the humidity of it. The basement is partially dirt and fieldstone/cinder block foundation so there is no plan to finish it off; it's just for storage, but as a result of the dirt floor, its pretty humid down there, especially during the summer months. My concern with the humidity is if I insulate the ceiling, will the insulation get moldy? What are my options in this situation?"

Answer: We recommend treating the basement like an unheated crawlspace. Place a 4 to 6 mil poly sheet over the dirt floor to keep ground moisture out. Then insulate the basement ceiling.

Install the insulation with the vapor retarder toward the warm side of the structure in heating climates such as yours. In a vented crawlspace, the warm side is usually up, closest to the floor. Once the insulation is in place between the floor joists, insulation hangers or nylon straps should be used to hold the product in place. Click on the word Crawlspace to see instructions for the project on the Owens Corning website.