[Greenbuilding] taping plywood seams vs. vapor barrier

John Straube jfstraube at gmail.com
Mon Jul 1 07:23:55 MDT 2013

Dense Pack Cellulose slows air relative to fiberglass but is a far cry from a reliable air barrier.  We have done lab tests on 4'x8' walls and the cellulose can do a remarkable job, BUT, it is not up to modern standards of airtightness.
Cellulose is a convection surpressing insulation
taped plywood is a kick ass rigid airbarrier.
water barriers sold as water barriers are great for their purpose.

On 2013-07-01, at 9:20 AM, Reuben Deumling <9watts at gmail.com> wrote:

> On Mon, Jul 1, 2013 at 5:44 AM, <jfstraube at gmail.com> wrote:
> Yes. It is critical to provide a water control layer!!!!
>  O.K. So what paper is recommended these days for a water control layer?
> All you have done by taping the plywood is produce an air barrier.  
> Which is a function I assumed dense pack cellulose was also achieving.  
> Building paper or a housewrap installed shingle fashion would be an example of a water control layer. Plywood is not.  
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John Straube

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