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I am bidding on finishing out a new basement with a prefab house above. There is to be a stud wall built around the entire exterior perimeter of the basement with bedrooms and a bath to be framed in also. My building materials sales man is telling me that I don't need to waste my time and money on putting a vapor barrier between the concrete walls and the stud walls with bat fiberglass insulation. His theory is to set the wall a half inch off the concrete wall and the paper backing on the insulation will act like the vapor barrier. But if the paper backing is not 100% sealed not just stapled in place, then the vapor barrier wouldn't be 100%either. To me that sounds like a disaster waiting to happen. I was thinking that there needed to be a vapor barrier in between the concrete wall and the stud wall, thus not allowing condensation to come in contact with the insulation and causing a mold issue. Either a poly film, a concrete sealer applied to the walls, or an asphalt impregnated product that is ran from the top of the concrete wall, down to the floor and under the bottom plate to help protect it. Also to protect the bottom plate one could use sill sealer under it to allow air and vapor flow? To seal the rim joist use spray foam on the rim and sill plate and rim and subfloor joints and then place faced fiberglass insulation into the joist opening? Any help would be appreciated, thanks