[Greenbuilding] taping plywood seams vs. vapor barrier

Alan Abrams alan at abramsdesignbuild.com
Tue Jul 2 07:22:27 MDT 2013


thnx for the informative report

On Tue, Jul 2, 2013 at 8:44 AM, John Straube <jfstraube at gmail.com> wrote:

> For those who dont know, ZIP is an OSB with a water resistant overlay
> bonded to it in the factory.  The joints are sealed in the field and the
> resulting assembly is an air and water barrier.
> We have tested it a fair bit and used it in construction.
> The air barrier is fantastic.  As good as almost any other approach.
> The water barrier is good except for the concern of installation of the
> tape at the horizontal joints. Workers can screw up and make fish mouths
> and other errors.  It is pretty good, but not as good as a gravity lap.
> Because of this concern, they have just launched a "liquid tape", a
> product with the consistency of peanut butter that you can smear into the
> joints and corners and penetrations.  Using this liquid flashing tape, I
> would rate ZIP better than almost any residential system I can think of out
> there.
>
> Re permeability.  The OSB in ZIP has the same permeance as normal quality
> OSB, that is, lowish.  About 0.3 to 1 under dry conditions (interior
> winter) and maybe 3 to 5 perms when damp (winter exterior conditions).  The
> exterior overlay that is added to render the system water resistant is
> about 16 perms, which is about normal for most house wraps.  We tested two
> walls side by side with high interior winter RH, one ZIP and one normal,
> and found the moisture contents of both systems to be about the same.
>
> RE tapes.  We have tested a bunch, as has Martin Holliday. We mostly were
> looking for tapes that stick to foam, which is easier in some ways than
> plywood, but move ore.  OSB, when clean and dry is easy to stick to. People
> want to believe that tapes are like cars, and that the only good ones are
> from Europe.  In reality, there are some top quality tapes made here, like
> 3M 3015, and Dow Weathermate, Dupont Straightflash. Most tapes sold here
> are not that good because they are cheap because people did not want to pay
> more than a few cents per foot.   If you spend 10 or 20 cents per foot you
> get good stuff.  Of course, products like ProClima and Siga are in the 50
> cents to $1/foot and are definitely good, but we have not seen a lot of
> benefits over the good ones at 20 or 25 cents cents/ft.  Wider tapes (2.5
> to 3+") are definitely useful and we see more and more manufacturers with
> wider tapes (e.g. 2" has been found to be practically too little)
>
>
> On 2013-07-01, at 9:53 AM, Alan Abrams <alan at abramsdesignbuild.com> wrote:
>
> > John S--
> >
> > what's your assessment of Zip Sheathing--as not only air barrier, but
> possible WRB.  Also, what about Zip's permeability VS plywood or OSB
> >
> > thanks-
> >
> > AA
> >
> > On Mon, Jul 1, 2013 at 9:31 AM, gennaro brooks-church <
> gennarobc at gmail.com> wrote:
> > I don't like any of the US tapes. Pro Clima from 475 here in the US or
> Siga are the only ones I would use.
> >
> >
> > Gennaro Brooks-Church
> > EcoBrooklyn.com
> > 347-244-3016
> > 22 2nd St., Brooklyn.
> > This email was sent from my phone.
> >
> > On Jul 1, 2013, at 9:24 AM, Reuben Deumling <9watts at gmail.com> wrote:
> >
> >>
> >>
> >>
> >> On Mon, Jul 1, 2013 at 5:53 AM, Sam Ewbank <g.l.ewbank at gmail.com>
> wrote:
> >>
> >> Rueben- One west coast supplier of SIGA brand tapes is Small Planet
> Workshop.
> >> http://www.smallplanetworkshop.com/siga-the-company-products/
> >> That stuff looks interesting. Thank you very much for the link.
> >>
> >> I've had good luck using 3-m 8067 all weather flashing tape around
> windows but don't know if it will last as long as the SIGA
> >> I'm happy to try that stuff too. Thanks.
> >>
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> >
> > --
> > Alan Abrams
> > certified professional building designer, AIBD
> > certified passive house consultant, PHIUS
> > certified passive house builder, PHIUS
> > Abrams Design Build LLC
> > sustainable design for intentional living
> > cell     202-437-8583
> > alan at abramsdesignbuild.com
> > www.abramsdesignbuild.com
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> John Straube
> www.JohnStraube.com
>
>
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>


-- 
Alan Abrams*
**certified professional building designer, AIBD
certified passive house consultant, PHIUS*
*certified passive house builder, PHIUS**
*Abrams Design Build LLC
*sustainable design for intentional living*
cell     202-437-8583
alan at abramsdesignbuild.com
www.abramsdesignbuild.com
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