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Separating blown cellulose from stem walls

fourforhome | Posted in Energy Efficiency and Durability on

I will be enclosing the bottom of the floor joist bays with poly iso and be blowing cellulose to fill the rest of the bay. The joists are hangered off the stem wall, so at the ends of each bay, the cellulose would be against the concrete.
I see here,, not to use polyethylene between the concrete and cellulose for a whole basement wall.
Is cutting and fitting some 1″ poly iso into every joist bay the best way to separate the cellulose from the concrete or could I get by with a little polyethylene in that space?
(Zone 4c, high radon potential/no conditioned crawl allowed, minimal/22″ crawl height).

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  1. GBA Editor
    Martin Holladay | | #1

    Either polyethylene or polyiso would work. I like the idea of the polyiso a little better -- I'd use foil-faced polyiso -- because polyiso has R-value.

    The situation you're worried about is an opportunity for condensation when the concrete is cold. The risk is low, but polyiso is the better solution.

  2. fourforhome | | #2

    Thanks, Martin.

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