Vapor barrier at interior high humidity locations?
Location: Ottawa, Ontario
Wall is 12″ thick R44:
2″ R8 EPS, zip system sheathing, 2×6 c/w R22 Rockwool, Intello+ interior smart vapour retarder, 2×4 c/w R14 Rockwool, interior finishing as specd
It is a limited vapour open wall in both directions.
I have a bathtub shower combo (acrylic base and acrylic surround), and a shower (acrylic base and tile over waterproof gypsum) against the exterior wall.
Given that these bathrooms will see elevated humidity should i add some 6 mil poly on the inside of the studs, between stud and the acrylic surround/waterpoof drywall? In these 2 areas of the house the concentrated vapour/humidity will not be able to cross the poly?
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Replies
Ryan,
This is a judgment call. If I were you, I would probably use interior polyethylene at the shower.
My take is that an exhaust fan will create negative pressure and stop humid air/water ex-filtration (which can move a lot of moisture quickly). For the short (I assume) time that it's super humid, not much diffusion will occur - without poly, it can dry inward over many hours of normal humidity.
Jon, I am using a balanced erv, so it wont have the moisture moving potential of a dedicated direct exhaust fan.