Zip vs. OSB and peel-and-stick?
I haven’t gotten local quotes yet for Zip system sheathing and tape (Canada), but from what I can see the Zip system would be slightly cheaper than using cheap commodity OSB and a peel-n-stick WRB like Adhero. Adhero might be a bit more labor intensive to install than the Zip tape as well.
Adhero is advertised at 8 perms, so would be less overall with the OSB. Not sure what the perm rating is for Zip, seems there’s some confusion there.
Any thoughts on going one way or the other? The OSB/Adhero route seems like it might make a more airtight structure? A more durable WRB? That’s just me guessing. Would it be any less risky than Zip from a durability standpoint?
Application would be in a 12″ cellulose filled double stud wall in CZ6A.
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Replies
Lance,
Q. "Not sure what the perm rating is for Zip, seems there’s some confusion there."
A. Zip System sheathing has a permeance of 2 to 3 perms -- about the same as ordinary OSB.
Thanks Martin. So I'm guessing Adhero wouldn't significantly reduce the permeability of the sheathing since it's 3-4x as permeable as OSB?
Lance,
Having built my own double stud wall house in a cold climate, I would skip the Zip and OSB and go with 5/8" CDX plywood. Tape the seams with Zip Tape (I loved Tescon Vana tape too) and then cover it with Tyvek and then add 1x3 strapping. So long as your siding is greater than 3/8" thick, your siding nails will never fully penetrate the precious plywood air barrier.
This assembly uses basic, cheaper materials and is vapor open. For added security- include a smart vapor retarder on the inside wall. If you want to get fancy- use Solitex Mento instead of Tyvek.
If you don't mind, how thick are your walls and what, if so, smart retarder did you use?
Walls are 12" . I used intello from 475 supply.
I personally like plywood over OSB but ZIP would likely be harder to screw up then tyvek for installers who are not conscientious net zero or Passivhaus builders.
Thats an opinion of course
Alan-
Yes! Our framers were amazing but they absolutely abused our precious WRB, eliminating any chances we had of using it as a second air barrier. I think you can make the plywood your air barrier and just treat the WRB as a rain barrier and still get a very durable/ air-tight wall. We used our smart vapor retarder as our secondary air barrier. In my opinion, this is the best place for your air barrier anyway.
> perm rating for zip
Less than 1 perm according to this (perhaps biased) source.
http://www.dupont.com/products-and-services/construction-materials/building-envelope-systems/articles/wall-sheathing-comparison.html
The plywood approach separates the functions of the air and water barrier. If they are combined, (like Zip) taping must be perfect to be a good water barrier, and there are a lot of taped seams. If the tape only has to stop air, taping defects are less consequential. Water barriers ideally follow the "down and out" approach. they should be shingled and open at their bottoms. This does not make for a good air barrier. House wrap has few critical seams to tape.
I contend that taped plywood covered by "loose" house wrap is more durable and more instillation fault tolerant than Zip.
Douglas Higden
I agree.
HI Lance -
1. I prefer rigid air barriers then flexible ones.
2. Perm rating for ZIP: The polymeric coating is about 13 perms or so; given that the OSB is in the 1 - 3 perms range (at about 25% moisture content; up to about 4 perms at 75% moisture content), the coating has negligible impact on the product overall permeance.
Peter