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Tyveck For Vapor Barrier?

 
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Old 02-21-2010, 12:47 PM   #21
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Re: Tyveck For Vapor Barrier?


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Originally Posted by tomstruble View Post
yea but i thought you didn't like to combine the two?And if ya think about it Lone maybe 2 layers of felt is a good idea under any siding not just stucco for the same ''wrinkly'' effect
Maybe that didn't read correctly. I prefer felt as opposed to plastic WRBs.
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Old 02-21-2010, 01:08 PM   #22
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Re: Tyveck For Vapor Barrier?


Granted, it's wet here, but we have new code: The new code change requires all new construction, some remodels and additions to install a drainage gap between the siding and the water resistive barrier.

There are exceptions, or alternative constructions. One of which are "enhanced WRBs." The EWRBs are basically dimpled or channelled roll goods. Another is sill pans that drain to the exterior of the veneer. (This one seems like an awfully easy "out.")

I am curious to see if everyone goes to the rain screens or opts for the alternatives.

Anyway, the conclusion was that none of the run of the mill WRBs, Tyvek, felt, etc., were doing enough for moisture control.

I did find some "science" comparing house wraps at:

http://bct.nrc.umass.edu/index.php/p...tion-barriers/
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Old 02-21-2010, 01:18 PM   #23
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Re: Tyveck For Vapor Barrier?


felt and foam...you no like? why is it so hard to understand me
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Old 02-21-2010, 01:21 PM   #24
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Re: Tyveck For Vapor Barrier?




http://www.buildingscience.com/doctypes/ (good starting point)

Bill, do you need or require a vapor barrier on the inside of your house in your area? If so Tyvek is a no-no, but there are many options available
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Old 02-21-2010, 01:22 PM   #25
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Re: Tyveck For Vapor Barrier?


Rory post those pics and that drawing of that foam install again if you get a chance
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Old 02-21-2010, 01:25 PM   #26
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Re: Tyveck For Vapor Barrier?


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Originally Posted by SLSTech View Post


http://www.buildingscience.com/doctypes/ (good starting point)

Bill, do you need or require a vapor barrier on the inside of your house in your area? If so Tyvek is a no-no, but there are many options available
This kind of goes along with the "close cell insulation" thread.

In our climate we have moisture inside half the year(winter 30-40% H), and moisture outside half the year (summer 70% H).

The walls here are sealed, in theory, poly inside and OSB/plywood and Tyvek outside.
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Old 02-21-2010, 01:34 PM   #27
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Re: Tyveck For Vapor Barrier?


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Originally Posted by MJW View Post
This kind of goes along with the "close cell insulation" thread.

In our climate we have moisture inside half the year(winter 30-40% H), and moisture outside half the year (summer 70% H).

The walls here are sealed, in theory, poly inside and OSB/plywood and Tyvek outside.
Are you stalking me today?

I know MN has poly inside, Alabama doesn't - I was asking if it was required in VA (where Bill is)

If you do require a VB inside - Tyvek won't cut it.

If you do use CC foam - you definitely don't need a VB inside as the CC foam is a vapor barrier. If it is thick enough condensation can't happen (it varies from 1 lift to 3 - aka 2" to 6" - the further north, the thicker it should be)
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Old 02-21-2010, 01:34 PM   #28
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Re: Tyveck For Vapor Barrier?


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Originally Posted by tomstruble View Post
felt and foam...you no like? why is it so hard to understand me
I prefer straight felt over sheathing. Not sure if their is adverse effects in conjunction with foam, especially unfaced, such as fanfold.
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Old 02-21-2010, 01:39 PM   #29
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Re: Tyveck For Vapor Barrier?


Tom,

I am not sure if I should re-post, but the thread you are talking about is
http://www.contractortalk.com/f33/bi...e-plank-72891/. That was all driven by the siding over foam thing.

For me, that build is novel because we used foam on the outside to let us avoid an interior vapor barrier, which is how this thread started.

Funny thing on the way to drywall. My BI looks at me with the standard WTF? look when I cite the code letting us skip the interior vb. Turns out, it's an IRC code compliant assembly, but that portion has not been adopted in Oregon, yet. They are planning on adopting it this summer.

So my interim option 1) is a low perm latex primer (less than 1.0 is compliant). But because I don't want an inside vb, I may go with option 2) which is a trip downtown on bended knee: hey it's IRC, DOE, BSC and this summer ORSC, so would you folks give us a pass on this one?

I suppose option three would be regular primer which is really very, very hard to distinguish from vb primer once it's on the wall, but that would not be very honest.
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Old 02-21-2010, 01:48 PM   #30
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Re: Tyveck For Vapor Barrier?


yea i prefer just have just ''paper'',but i am starting to be able to see the advantages in a foam thermal break,but installing it after the windows and doors are in makes it harder to to detail the drainage plane

maybe a better detail would be to install the foam directly to the studs and get the wood sheathing out of there...i don't know
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Old 02-21-2010, 01:54 PM   #31
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Re: Tyveck For Vapor Barrier?


Quote:
Originally Posted by tomstruble View Post
yea i prefer just have just ''paper'',but i am starting to be able to see the advantages in a foam thermal break,but installing it after the windows and doors are in makes it harder to to detail the drainage plane

maybe a better detail would be to install the foam directly to the studs and get the wood sheathing out of there...i don't know
Tom, whoever built the 2nd floor on my house used shear panels in the corners with 1/2" foam over, then infilled with 1" EPS. T-111 overtop with no other WRB. As you know, I felted over it and installed vinyl. I have had 0 moisture issues before the vinyl and so far, none after. I'd be more concerned if I had used a plastic WRB, but that's just me.
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Old 02-21-2010, 02:12 PM   #32
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Re: Tyveck For Vapor Barrier?


yea there is a developement around here that used foam sheathing
but no wrb and masonite siding and trim you can imagine how long that held up
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Old 02-21-2010, 02:27 PM   #33
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Re: Tyveck For Vapor Barrier?


I don't know if we need a new thread (does wandering from inside vbs to outside vbs to foam and siding constitute a thread hijacking?), but..

First I will say that I would love to get a job where I get to try a build w/out wood sheathing. Very sexy, very "advanced framing," etc.

However:

I don't think that eliminating the plywood is going to make installing anything on top of it any easier.

If you can meet the engineering/shear/seismic side of the equation, and you are only using foam sheathing for much/most of the walls, wouldn't the seams on the foam be a bear w/out a solid surface behind them? Wouldn't it be pretty hard to land two pieces on the same stud? Or do you stagger the seams "off stud" and rely on the T&G in the "air?"

And now my WRB is only getting nailed every 24" oc. That seems light too. Better side that pretty quick.

Last, I thought that the foam manufacturers spec'd the wrb behind the foam? I will have to dig around for info on that.
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Old 02-21-2010, 02:48 PM   #34
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Re: Tyveck For Vapor Barrier?


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Originally Posted by Rory Read View Post
First I will say that I would love to get a job where I get to try a build w/out wood sheathing. Very sexy, very "advanced framing," etc.

However:

I don't think that eliminating the plywood is going to make installing anything on top of it any easier.
I've framed dozens of houses that, due to fire code, only got shear panels in the corners and let-in metal bracing wherever it was practical. The wall was infilled with 5/8 "gyp-lap" sheathing. Then along came the tie-down straps that had to be 4' long, tying the first floor studs to the second and 3' to tie in the first floor studs to the rim. This made it next to impossible to install vinyl siding, so the shift went to fire rated CDX. I've also framed homes with plywood shears, infilled with foil faced foam. With vinyl over, it's not the most secure wall construction.
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Old 02-21-2010, 02:49 PM   #35
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Re: Tyveck For Vapor Barrier?


Rory - I don't think it needs a new thread, the problem is most people do not fully understand how the whole system ties together - your sider knows X, you insulation contractor knows Y, etc... Then we start adding in which climate your in and let the good times roll

As for foam only exteriors, no thanks - first major down burst or straight line winds coming in, I am sure a few people will be surprised when they find their patio furniture inside the house. Give me the good ole plywood or OSB with foam over it or better yet CC behind it anyday.
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Old 02-23-2010, 01:45 PM   #36
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Re: Tyveck For Vapor Barrier?


I have also thought about using tyvek INSIDE
for an unventilated flat roof.
99% of interior moisture that enters the walls and ceiling is through
air leaks.
An air barrier is all that is needed to stop air leaks so tyvek should be suitable.
Because its vapor permeable, the tyvek covered walls/ceilings can have a chance to dry out in the warm season. This is especially important for unvented flat roofs that can only dry inwardly.

Typically sheetrock installed in an airtight manner is used for this purpose
but the tyvek sure sounds easier to hang and without adding any weight.
My 2x8 rafters look weak enough that I'd be afraid to add the weight of sheetrock.

Tyvek against the rafters with a dropped ceiling below that. How does that sound?

This is zone 5 with about 5800 hdd (heating degree days) so poly plastic VB is not strictly needed. I'd rather have the enhanced breathability.
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Old 02-23-2010, 02:12 PM   #37
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Re: Tyveck For Vapor Barrier?


tyvek actually has an attic wrap designed specifically for that
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Old 02-23-2010, 02:21 PM   #38
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Re: Tyveck For Vapor Barrier?


i agree not haveing ply would suck but it seems to be the weak link in the whole foam/insulation wall sandwitch thing,whats needed maybe is a truely nailiable insulated wall panel,like a sips panel but thinner
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Old 02-23-2010, 06:38 PM   #39
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Re: Tyveck For Vapor Barrier?


Quote:
Originally Posted by loneframer View Post
Tom, whoever built the 2nd floor on my house used shear panels in the corners with 1/2" foam over, then infilled with 1" EPS. T-111 overtop with no other WRB. As you know, I felted over it and installed vinyl. I have had 0 moisture issues before the vinyl and so far, none after. I'd be more concerned if I had used a plastic WRB, but that's just me.
Quote:
Originally Posted by tomstruble View Post
i agree not haveing ply would suck but it seems to be the weak link in the whole foam/insulation wall sandwitch thing,whats needed maybe is a truely nailiable insulated wall panel,like a sips panel but thinner
Plywood (T-111)over the EPS panels worked fine for 20 some years before I sided over it. I used 2 1/2" roofers and stud-nailed, along with some others placed to center the panels.
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Old 03-07-2010, 04:59 PM   #40
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Re: Tyveck For Vapor Barrier?


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Originally Posted by Rory Read View Post
No matter where you live, you want the wall to breathe in at least one direction or the other. You have to figure what makes sense for your climate. After you decide that, then you decide where vapor barriers and retarders go and what your ideal wall construction looks like.

Try the DOE for regional guidance:

http://www1.eere.energy.gov/building...lications.html
Nice link,thought I'd open it an do some light reading. 139 pages! Guess I have to sit down with a beer or two for that one. Definately going to check it out though.
thanks

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