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Insulating the interior of a basement wall that has existing 1″ foam board on the outside of the wall

kZae5TDdoP | Posted in Energy Efficiency and Durability on

I plan on finishing off the basement of a 1970s house. This house has poured concrete walls with 1″ XPS foam board on the outside of the basement wall (down to the footings) with foam also on the rim joist. Will installing 2″ XPS on the inside wall and rim joist cause problems?


  1. GBA Editor
    Martin Holladay | | #1

    Q. "Will installing 2" XPS on the inside of the concrete wall cause problems?"
    A. No.

    Q. "Will installing 2" XPS on the inside of the rim joist cause problems?"
    A. No -- as long as the rim joist has no signs of water staining, mold, or rot (any of which might indicate a water entry problem from the exterior).

  2. kZae5TDdoP | | #2

    Thanks, Dan

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