[Greenbuilding] [BULK] Re: And the debate rages on to add an air barrier or not to air barrier!
Lawrence Lile
LLile at projsolco.com
Fri Feb 1 16:01:44 CST 2008
I vote for the Tyvek. OK, if you do get water penetration, without the fabric, then what? Tyvek is a continuous drainage plane, nails or no. It is cheap, and if you need it, you need it. If you don't, it is an additional measure against infiltration. SOlve indoor air problems with ventilation and energy recovery ventilators, not by making a crappy wall, that's my 2c.
--Lawrence Lile
-----Original Message-----
From: greenbuilding-bounces at listserv.repp.org on behalf of William R Bloom
Sent: Thu 1/31/2008 6:07 PM
To: Joshua Lloyd; John Messerschmidt; Greenbuilding at listserv.repp.org
Subject: [BULK] Re: [Greenbuilding] And the debate rages on to add an air barrier or not to air barrier!
Hi Joshua:
Its not really the face that is penetrated with fasteners
that provides the barrier. Based on the construction, I'm
assuming you are working on a commercial structure rather
than a residential one. In residential construction,
rather than the exterior gypsum sheathing (for a fire
rated listed assembly?) you would typically see an
insulated panel such as celotex, usually with some kind of
shear value, or celotex with oriented strand board at the
corners for shear. With this construction, the residence
is wrapped in tyvek to prevent infiltration. The
infiltration occurs primarily at the joints, not the face,
so all the fasteners on the face have minimal effect on
infiltration, its where the tyvek covers the sheathing
joints, where the floor to floor joints are. Usually they
don't fasten right on the joints, so there is a perceived
barrier. Now with residentail construction, Group R
occupany usually doesn't require active ventilation. The
10% glass 5% vent per room meets the code. When I built
my house outside of Detroit, I opted to go without the
wrap to prevent poison house syndrome. If you are working
commercially, there is probably an air handler with a
certain percentage of outside air introduced by the system
set to comply with occupancy.
So the real benefit would be to prevent infiltration in a
structure where active infiltration is designed in anyway.
If you are taping the joints, that would have the same
effect, actually better, than if the tyvek spanned the
joints?
Bill Bloom
Former Detroiter
Now Sunny New Mexico
On Thu, 31 Jan 2008 18:28:35 -0500
"Joshua Lloyd" <JLloyd at markwoodarch.com> wrote:
> John,
> I have to pick my battles. It is what the "old guys"
>wants. However
> the batts are manufactured only 50 miles from the site.
> So a minimal
> transportation footprint. But I do have 1/2 lb open
>cell spray applied
> foam in the specs as an alternate. So if we can just
>quantify the extra
> cost, I believe it will be a go.
>
> And I agree with you about the Tyvek. I think the same
>thing about
> Asphalt shingles. Especially after renovating my home
>and doing most of
> the work myself. We call it weather resistant, yet we
>riddle it with
> holes and hope the overlap is enough.
>
>
>
> -----Original Message-----
>From: John Messerschmidt [mailto:john at ducecc.com]
> Sent: Thursday, January 31, 2008 6:11 PM
> To: Joshua Lloyd; Greenbuilding at listserv.repp.org
> Subject: RE: [Greenbuilding] And the debate rages on to
>add an air
> barrier or not to air barrier!
>
> Joshua,
> I never got how Tyvek or the rigid insulation could be a
>vapor (or
> weather) barrier if you have to nail through it to
>attach the siding.
> But besides that, why do you want to use fiberglass
>batt? Yuk.
>
>
> John
>
>
>
>
> -----Original Message-----
>From: greenbuilding-bounces at listserv.repp.org
> [mailto:greenbuilding-bounces at listserv.repp.org] On
>Behalf Of Joshua
> Lloyd
> Sent: Thursday, January 31, 2008 6:09 PM
> To: Greenbuilding at listserv.repp.org
> Subject: [Greenbuilding] And the debate rages on to add
>an air barrier
> or not to air barrier!
>
> Ok, I am hoping that I can get some educated help on
>this topic for we
> are going around in circles with this issue in our
>office. We are
> working on a project here in Central Ohio (Climate Zone
>5) and we are
> trying to increase the performance of our exterior wall
>so we currently
> have the following assembly:
>
> Brick Veneer
> 1" air space
> 1" Foil faced Polyisocyanurate
> 1/2" Exterior Gypsum Board
> 6" Metal stud w/ Unfaced Fiberglass batts 5/8" Gypsum
>Board Latex Paint
>
> Now the question is; Do we need to add a weather
>resistant barrier (ie.
> Tyvek) between the foil face rigid board insulation and
>the exterior
> gyp. board if we are taping and sealing all the joints
>of the rigid
> board insulation? It is my understanding that the
>weather resistant
> barrier at this point is solely used as a drainage plane
>if water was to
> penetrate through the rigid board. But if we are taping
>and sealing, I
> don't see the need for the drainage plane because the
>rigid insulation
> will be acting as that drainage plane.
>
> What are your thoughts on this?
>
>
> Joshua Lloyd
> Assoc. AIA, LEED AP
> Phillip Markwood Architects, Inc.
> 240 North Fifth Street
> Suite 140
> Columbus, Ohio 43215
> Ph: 614.461.8300
>Fax: 614.461.8302
> email: jlloyd at markwoodarch.com
><blocked::mailto:jlloyd at markwoodarch.com>
>
>
>
>
>
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