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Above Slab Vapor Barrier Needed?

drrenken | Posted in Energy Efficiency and Durability on

I am just outside Atlanta and I am planning on insulating on top of my new construction slab with 1″ XPS (cheap marketplace find), two layers of 3/4 subfloor and then 3/4 hardwoods. Going this route for a couple of reasons, but my question is do I need to do a vapor barrier underneath the XPS? I do have a 15 mil vapor barrier underneath the slab. Thanks!

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  1. Expert Member


    A concrete slab needs a vapour-barrier. I you have an effective one below the slab, you don't need another one above.

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