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Condensation between interior foam and concrete wall?

Michael Schonlau | Posted in General Questions on

Will condensation occur on the interior side of a concrete foundation wall that is built with 2″ of rigid foam, studs, fiberglass batts or cellulose in the cavity, and drywall? We are in Omaha, NE. If so, what should be done to prevent the condensation?

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Replies

  1. John Klingel | | #1

    #1. Exterior measures (dirt grade, gutters, etc) to minimize the potential trouble of water in the first place.
    #2. "Water proof" the outside of the concrete wall.
    #3. Insulate outside the concrete.
    #4. Air seal the inside sheathing, and make sure it is vapor open, w/in code requirements.
    #5. I don't think you'll find that fiberglass batts are the best choice for basements. I don't think they are the best choice for anything. Rock wool seems a better alternative.
    #6. Check on buildingscience.com. I am no expert, but those are the things I have gleaned from available, reputable sources.

  2. GBA Editor
    Martin Holladay | | #2

    Michael,
    Q. "Will condensation occur on the interior side of a concrete foundation wall that is built with 2" of rigid foam, studs, fiberglass batts or cellulose in the cavity, and drywall?"

    A. No -- as long as you make sure that the foam is installed in an airtight manner. Tape or foam the seams between the foam sheets, and use caulk at the perimeter of the sheets.

    But the fiberglass batts (or cellulose, for that matter) would be a bad idea. If you want a higher R-value than is provided by 2 inches of rigid foam, just make the foam thicker (or install two layers of foam). Your stud bays should be left empty (except for electrical wiring).

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