Interior poly vapor barrier
lad58
| Posted in Energy Efficiency and Durability on
I’m considering fiber cement siding and drainable house wrap for my 1994 house in coastal South Carolina. In 94, the builder installed a poly vapor barrier between the wallboard and the studs throughout the house. Based on my reading on this great website, I believe the wall assembly, which is OSB, covered by a disintegrating house wrap and vinyl siding, must dry to the outside. I would like to use a low perm house wrap due to the hot, humid climate, but I’m concerned that would affect the ability to dry to the outside.
Any insight would be appreciated.
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Replies
lad,
The big worry with interior poly in warm, humid climates is during the cooling season when it becomes a wrong side vapour-barrier, and can have moisture condense on it.
OSB is about 2 perms when dry and opens up to about 12 perms when damp, so it will probably be what limits drying to the outside, even with a low perm WRB.
Thanks Malcom. We recently opened a couple of walls during a renovation and the osb was fine. So I guess the wrb should not be an issue
lad,
That's good news. I think you will be fine.