Lori writes from Houston, Texas: "I have an all brick exterior house in Houston, TX built in 1950's. Brick appears to be up against exterior black sheathing. The house is being completely remodeled with R-15 unfaced insulation in exterior walls and R-30 unfaced insulation in ceiling/attic of the one story house. Is it necessary to put a vapor barrier (.6 mil plastic sheet) between insulation and finished drywall in Houston, Texas climate or will this be creating a moisture problem?"

Answer: Our recommendation is to have a vapor retarder on the warm-in-winter side of the wall assembly, which is where you indicate you will place it. Because Houston can be very humid, you will want to check with your local building code to see if it has a recommendation for your area. If the local building code does say polyethylene is a recommended application, I recommend using a 4 mil sheet unless the code recommends otherwise. Six mil polyethylene is a very strong vapor retarder. You will want to condition the living space to help prevent moisture buildup.