Lou writes from Douglassville, Pennsylvania: "I thought I understood how to properly place foam insulation and vapor retarder, but a few posts have me confused! I've read that plastic vapor retarder is not recommended in the basement because it is too strong for the amount of moisture. I have also read that rigid foam should not be used as a sole vapor retarder. So if i wanted to use rigid foam on the walls and the floor, as well as rolled insulation in between metal studs, what should I do about a vapor barrier? Should I use non-faced insulation, kraft faced insulation?"

Answer: FOAMULAR® insulation is not a vapor retarder. Although extruded foam insulation has the characteristics of a vapor barrier, it cannot solely act as one. If you have multiple products with vapor barrier characteristics, you need to place the strongest vapor barrier nearest the warm air.

For basement applications, thicker foam is generally used, such as 1.5 or 2" InsulPink® extruded basement wall insulation. Please check with your local building code for more information. There is also information on the Owens Corning Web site about InsulPink insulation and proper basement installation using an extruded polystyrene (XPS) insulation.

Also, you are correct; Owens Corning does not recommend using poly vapor retarders over its insulation products in a basement because the poly is too strong and can trap moisture.