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Another poly question (ceiling)

canadianexpy | Posted in General Questions on

I have been told told by the builder to expect to have poly required  by the inspector on the ceiling and walls. (Ontario Zone 6) I will be using mini splits for heating and cooling, so yes A/C in the summer. My question is if regular 6mil poly will be any issue on the ceiling?
Its a vented attic space that will have minimum R60 blown in cellulose.
As for the walls I plan on using Smart Membrane, if I can’t convince them otherwise, as I have 6″ of polyiso on the exterior.

Thanks Dave
Zone 6 Ontario

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  1. Yupster | | #1

    In Ontario, builders are pretty familiar with installing poly as an air barrier. Even though they often don't know that's the function it's performing, they do know it needs to be sealed and have gotten pretty good at it. The only downside to using poly in a vented attic like yours is that it's still hard to get it perfect. Minimize penetrations and make sure they get sealed well. Holes drilled in top plates often end up in no-mans land, so you might have to get those ones yourself. Also, even the airtight boxes commonly used here aren't airtight without some additional caulking, so be prepared for that. Use acoustical caulk for sealing, not tape.

    1. canadianexpy | | #2

      Thanks Yupster, always helpful.
      I plan on using acoustical sealant, airtight electrical boxes and I will be dealing with top plate penetrations. The framer fasten poly between top and bottom plates through out the house.
      I was just making sure no issues with installing the poly on the ceiling, I could not think of any since its only cellulose and unconditioned air on the other side. Just wanted to make sure..
      I hope to use drywall as my main air barrier on the ceiling .

      Thanks Again

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