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Poly under panelling ?

I have a camp that I use mostly in the summer, but some in the fall/winter, that I have: insulated the floor, will spray foam the cathedral ceiling, rebuilt the walls with (outside – in) 19/32” T1-11 sheets (stained), 1 x 3 strapping (vented air space), Tyvek house wrap, 7/16 OSB, 2 x 6 studs, Roxul R24. And now I’m stuck. I have read many (most) of your articles, etc. on vapor barriers, permeability, etc., and if I understand correctly, I should not install a poly barrier, and go with primed and painted drywall, however, I would prefer for simplicity sake to go with 4x8 sheets of panelling. Any thoughts on how I could successfully keep moisture out of the wall cavity if I use panelling / other suggestions? Thanks.

Asked by David Beals
Posted Jul 1, 2014 9:59 AM ET


2 Answers

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1. Where are you located? What is your climate zone?

2. Vapor diffusion almost never causes moisture problems in walls. However, paying attention to airtightness is important. If you plan to install 4x8 sheets of paneling on the interior of your walls, make sure that you use a continuous bead of caulk or adhesive around the perimeter of each sheet when you install the paneling. It's also a good idea to use airtight electrical boxes.

For more information, see these articles:

Vapor Retarders and Vapor Barriers

Forget Vapor Diffusion — Stop the Air Leaks!

Do I Need a Vapor Retarder?

Answered by Martin Holladay, GBA Advisor
Posted Jul 1, 2014 10:54 AM ET


Thanks for the quick reply Martin. I am a huge fan of your work.

I am located in Ontario, Canada (in between Ottawa and Toronto) (Zone 6)

I have installed poly vapor barrier boxes around each of the receptacles, and will seal them well. I presume I should caulk these to the panelling too.

Thanks again!

Answered by David Beals
Posted Jul 1, 2014 11:18 AM ET

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