Ok, Here is the deal. We are going to be doing an addition to a log home. We will be using an existing decks framing for the floor framing of which is about 12 foot from the ground. When complete the room will be insulated, floor walls and ceiling and under heat and air. The underside of the floor will be sealed with Tyvek and 1/2 plywood. The HO want to use sheet flooring in this room. They talked to a local flooring merchant that told them they may have a mold problem (on the underside of thhe sheet product) due to changes in the floor temp. Is this true and if so what can be done to eliminate the problem?