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Is it advisable to install foam on the interior of an insulated stud wall?

April 26, 2017advisable foam install insulated interior stud wall

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Is it advisable to install foam on the interior of an insulated stud wall?

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Bill writes from Haslet, Texas: “We are building a home in San Antonio, TX with a stucco exterior (hand-applied, not sprayed). Is it advisable to install 1″ foam on the INTERIOR side of a 3.5″ Fiberglass insulated stud wall? Is OC foam board a vapor barrier/retarder; I believe in our climate the vapor barrier should be installed on the outside wall.” Answer: FOAMULAR® insulation is commonly used as an interior sheathing on above-grade stud walls. FOAMULAR insulation is not classified as a vapor barrier/retarder. If you want more R-value in an exterior wall, Owens Corning recommends placing 1″ FOAMULAR 150 insulation board as sheathing over the studs on the warm-in-winter side of the wall and then cover it with drywall.