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Community and Q&A

What is the best way to insulate basement exterior walls that have a minor problem with condensation?

DJ Tejeski | Posted in Green Building Techniques on

This house is in the Philadelphia area and the foundation walls are constructed with CMU. The condensation occurs intermittently in the springtime months.


  1. GBA Editor
    Martin Holladay | | #1

    You need to install interior insulation. Your best choices are rigid EPS foam, rigid polyiso foam, or closed-cell spray polyurethane foam.

    In your climate zone (either zone 4 or zone 5), the 2006 IRC calls for a minimum of R-10. That means about 3 inches of EPS, or about 2 inches of polyiso or closed-cell spray foam.

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