Correct place for Vapor Barrierr

Old 01-13-16, 03:59 PM
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Correct place for Vapor Barrierr

Hello, I am remodeling a room and have the floor down to bare floor joists. i'm trying to determine the best location for a vapor barrier. The finish floor will be Fossilized Bamboo over 1/2" and 3/4" plywood. The room sits over a partial basement or crawlspace with a concrete slab. About 4' from top of joists to concrete floor, the space is connected to a full basement so its around 55 degrees in winter. it is dehumidified in the summer as the main basement is 1850 vintage. Any advise would be appreciated.

Old 01-13-16, 05:08 PM
Join Date: Oct 2008
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Hi AB and welcome to the forum. Unless the mfg of that Bamboo suggests a vapor barrier, you application over wood over a partially conditioned crawlspace does not seem to require one. If used, you would normally install one on the warm side of the assembly, but those assemblies include a thermal barrier, insulation. In an exterior wall, that insulation keeps the outside surface above the dew point eliminating the risk of condensation. Your floor will not be seeing dew point temperature levels so any moisture movement will not be an issue.

Insulate the exterior joist and address any air leaks you can, like the bottom of the drywall.


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