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Obscure OSB air barrier questions

In general, is an air barrier composed of 7/16" OSB similarly effective as a 5/8" OSB air barrier, assuming all installation details were the same for both?

I have seen people using caulk and without caulk when fastening OSB to structural lumber, I assume that the concept with the caulk is that they're trying to seal the penetrations through the OSB?

Are the air leakage through holes created (and filled) a significant source of air leakage?

Thanks,

Chris

Asked by Chris Barnes
Posted Mon, 12/09/2013 - 17:29
Edited Tue, 12/10/2013 - 07:15

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3 Answers

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1.
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Chris,
Both thicknesses of OSB perform equally well as air barriers.

The easiest way to create an air barrier with OSB is to tape the seams -- not use caulk.

You don't have to worry about air leaks at the fasteners (especially if you tape the seams).

Any penetrations (wires, pipes, etc.) need to be sealed with caulk, canned spray foam, or tape.

Answered by Martin Holladay, GBA Advisor
Posted Mon, 12/09/2013 - 18:02

2.
Helpful? 0

Just to be clear, I meant caulking where the OSB is fastened to the structural lumber, not caulking at the seams. What is the purpose of caulking this area if the seams are taped/filled? (I saw this in the passive house video linked on the front page, and discussed elsewhere..)

Anyways, thanks for the feedback!

Answered by Chris Barnes
Posted Mon, 12/09/2013 - 18:12

3.
Helpful? 0

Chris,
If you're planning to tape the seams between your wall sheathing panels, I don't think that you need to use caulk between the sheathing and the studs or plates. But some Passivhaus builders use caulk plus tape as kind of belt-and-suspenders approach. Needless to say, these projects often have high budgets.

Answered by Martin Holladay, GBA Advisor
Posted Mon, 12/09/2013 - 18:19

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