David writes from Louisville, Kentucky: "We recently discovered mold in our finished basement on the surface of the drywall at the bottom behind the base board molding on two exterior walls and on the back side of the drywall of the same walls. The basement was finished 28 years ago. My friend and I put on our Biohazard suits and went in this weekend and removed the drywall. We also found some mold between the poly barrier and the insulation. We removed all of the affected poly and the insulation. The mold appears to be entering from inside the room as no source of outside moisture appears to be present i.e. no moisture on the studs or stains from a leak. The people that owned the house for 28 years prior to us moving in never had a dehumidifier and checking the humidity level of the basement it appears high, around 60% this week outside humidity is running about 45% in our area.

"My question is, do we replace the poly and insulation with un-faced insulation and new poly or use just use Kraft-faced insulation? Keep in mind that on most of the walls only the bottom half of the wallboard had to be removed since the mold stopped about 12 inches from the bottom of the floor and that the old insulation and poly will remain in the drywall on the upper part of the wall. The house has a pressure treated wood foundation with a concrete slab instead of the conventional poured concrete foundation that is more prevalent in our area. It also has poplar siding that has been covered with foam and vinyl siding. The area of the basement being replaced is a walk-out with a sliding glass door has a cold air return and two ceiling registers. We plan to replace the removed drywall with either Mold Tough Sheetrock or Georgia-Pacific DensArmor Plus paperless drywall and install a dehumidifier to help prevent mold in the future."

Answer: We recommend installing Kraft-faced insulation. We also recommend checking your local building code for information related to the use of poly in a basement. If there is a moisture issue in the walls, it is generally not a good idea to use a poly because it is too strong of a vapor barrier. We recommend using a weaker vapor retarder such as Kraft paper so the cavity can breathe somewhat.