Polyethylene sheet trapped between gypsum and wood panels: Is that wrong?
Hi everyone,
I am currently restoring an old house in a cold climate. The ceilings on the second floor were previously covered with big fiberboard panels, which I removed because they looked wavy. Under it is a layer of old wood paneling (V-joints), that used to be the finished ceiling before, which are fixed to the attic studs. Directly on top of them, in the attic, is the current insulation (looking like cellulose).
The wood paneling is too damaged to be kept visible but I don’t want to remove it (mainly to avoid the mess) so I want to recover it with gypsum panels. Now the question is : would it be right if before fixing the gypsum I cover the wood paneling with a sheet of polyethylene to act as a air-vapor-barrier?
I’ve never heard before situations where the polyethylene is trapped between two layers of “solid” before reaching the insulation, but for me it looks like it may do its job since it is always on the warm side, right?
Otherwise, would the gypsum with a good paint be sufficient to act as an air-vapor-barrier?
Thanks a lot,
Baril
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Replies
Baril,
Although you told us that you live in a "cold climate," you weren't very specific. Are you talking about Pennsylvania or Fairbanks, Alaska? Climate matters.
In most of the U.S., a layer of interior polyethylene on walls and ceilings does more harm than good -- especially if the house is air conditioned during the summer. More information here:
Do I Need a Vapor Retarder?
Vapor Retarders and Vapor Barriers
Forget Vapor Diffusion — Stop the Air Leaks!
In the colder parts of Minnesota and Canada, you can get away with an interior layer of polyethylene -- especially if you are fairly sure that the house will never be air conditioned during the summer. But it's safer to omit it.
Every wall and ceiling always needs an air barrier. Gypsum wallboard is a perfectly good air barrier; just pay attention to sealing leaks at penetrations and electrical boxes, and you'll be fine without the poly.
Thank you Martin. FYI I live in Ottawa (Canada), so no need of poly I suppose. Sounds good to me then.
I'll put a plastic barrier around my light/electric fixtures and some tuck tape all around the edges, that should be enough.
Once again, thanks for the quick reply!