Question:

Hi, I want to to insulate a roughly 8' x 8' basement area under a small room which is not heated although there appears to be minimal insulation. The 8' room is concrete walls and floor and has a small window which does not open. My plan is to cover all walls entirely with the Dupont foam board, build the studs, stuff fiberlass in between and put a vapour barrier over the walls, then add the 1/2" drywall. Does this sound correct and what about the concrete floor? I was thinking fiberglass and 1/2" plywood on 2 x 4 studs 14" apart.Can you please advise? Thanks//gerry sweeney //GTA

Answer:

Hi Gerry, I want to advise you that the foam board you are using being that it is a closed cell polyextruded styrene acts as its own vapor barrier so I would advise against placing insulation on top then a vapor barrier, because if you did what meantioned in doing you would have 2 condensing plains where moisture can accumulate, so in saying that your vapor barrier should always be on the warm side. Having double vapor barrier is a no-no as is will lead to rotting out of the framing and worse mold. I would advise on using one insulation or the other at the thickness you desire, code requires at least R12 in the basement. The concrete basement floor is rarely insulated but if you choose to a somewhat common practise is to lay the polyextruded styrene in between the subfloor, do not do this if it is between floors where there is a living space below. Comfort Insulation 613-226-9912

Answered By: Sam Marrello

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