Attic and Poly Question

Why isn’t there a poly to act as a air/vapor barrier between living space and attic? I read that if there is too much venting in the attic, it can create a negative pressure drawing warm most air from the living space up in the attic. Also if there isn’t enough insulation, warm moist air is again a problem going in the attic. Why not have a polyethylene on the ceiling after the drywall like on outside walls?



It was not always this way, When was the home built?

Hi, it’s a general question for new homes. Thanks.

It should be installed on warm side of insulation. Walls and ceilings in all of Canada. It goes on right before drywall goes up. Not all city’s require a poly inspection for code compliance, but a quick look on the Burnaby website indicates they do have a poly stage inspection before drywall goes up. It has been a code requirement to have since late 80’s I belive.

On the ceiling? I know about outside walls but I never see it on the ceiling and was wondering why. Thx


Here these are from another thread today. :wink:

They must do things differently in BC :slight_smile:
Alberta houses have poly on the ceilings under the attic.
Even my 1951 house has a sort of wax paper over the plaster ceiling.
Without looking it up, the code probably specifies vapor barrier, with a minimum number of perms.
There are other ways to accomplish that without using poly.
Talk to a home builder or code inspector in your area to get the real story, not likely that builders are not following code, given the problems that BC has been having with condos and such.

I would check building code… but it sure is required in Ontario… and I suspect in BC as well.

Do they insulate the ceilings… if so should have vapour barrier.

Do they insulate the ceilings… :slight_smile: if so should have vapour barrier. No, seriously they are supposed to have it.



I have insulated homes in 5 different provinces. It is always required in new homes and has for quite some time.

At what stage are you looking for it? Digging through blow in insulation during inspection?

If the installer put the poly on real tight and straight without wrinkles, and you are looking for it from the attic digging through blown in cellulose with a weak flashlight… yeah you might not see it readily. :smiley: