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Community and Q&A

Vapor barrier location in ICF construction?

GBA Editor | Posted in General Questions on

When using ICF construction for walls that run to the rafters and you would like to construct an interior wall for electrical and other services where do you place the vapour barrier if any any?

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  1. User avatar GBA Editor
    Martin Holladay | | #1

    An ICF wall has no need of an additional vapor retarder. The ICF wall is basically invulnerable to moisture, and it dries readily in both directions. You will have no condensation problems in your stud wall.

  2. Riversong | | #2

    An ICF wall might be invulnerable itself to moisture, but its concrete core can wick moisture up from the footings unless there is a capillary break between footings and wall. If it does wick significant moisture, then that moisture can be driven by summer temperature and vapor pressure differentials into the interior wood-frame walls where warm conditions will be conducive to mold growth.

    But I agree that no additional vapor retarder is necessary as long as you control indoor relative humidity with source extraction and controlled ventilation.

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