Tyvek under 1/4in foam for Vinyl siding? - Contractor Talk - Professional Construction and Remodeling Forum

PittTrack · 02-09-2009, 01:26 PM

I've lurked for a while and on some questionable topics found what I needed via searching. This time I have searched and came up with nothing so I figured why not post it.

Having said that we are working on a house that was built in the late 70's and appears to have some sort of black (not roofing tar paper) reinforced wrap under the existing aluminum siding from the few small pieces that we took off. We are replacing the windows with new construction windows and some of them will be slightly smaller than the existing openings (by ~6" total in width). After we sheath on the exterior to get the heights to be the same we were going to use the 6in PSA Opti-Flash on the fins which will then cover the ~3in of exposed sheathing and 3" of black hose wrap. After that we were going to cover the black house wrap with 1/4in blue foam and tape all of the seams then proceed to start siding.

The homeowner asked if we should pull the siding off, put a Tyvek housewrap on the house, then put the windows in, and seal with the 6in PSA Opti-Flash and then put the 1/4in blue insulation over that with taping the seams on the blue foam.

I thought it made sense at first but I keep going back and forth to if it will trap the moisture between the tyvek and the foam meaning that we should just put the foam over the existing black stuff and call it a day or if we should wrap the house with tyvek.

The siding sub insists on doing the house with the 1/4" blue foam inorder for labor warranty. On other houses we've done (for years) it's never been a problem with his labor or product.

So what's your thoughts on if we should use Tyvek or not?

TIA

tcholdren · 02-09-2009, 01:38 PM

always remove the tar paper, news paper, rosyn paper what ever they used! its not letting the home "breath'. always install insulation board first then house wrap. if you dont, condensation will happen because you are trapping the air behind the foam board.

BirmanBuilders · 02-09-2009, 01:43 PM

I'm with tcholdren on this one.

PittTrack · 02-09-2009, 01:52 PM

Would it make more sense to either:

A) Remove the black paper and then Tyvek the house, install siding w/out the 1/4 insulation

B) Remove the black paper and then install 1/4in insulation and side house?

I would say to insulate and then tyvek but the vinyl guy don't want to make multiple trips. I personally am leaning towards option A as it gives me a vapor barrier and seals the house up. I also don't see how much value the 1/4 insulation provides.

tcholdren · 02-09-2009, 02:02 PM

A is your best bet, but tape your seems. adding the insulation really varies where your at in the country down south 1/4" is cool up here in the north 3/4" OR THICKER. good luck

Grumpy · 02-09-2009, 02:49 PM

We have tried installing the tyvek after the insulation and have had poor results. I find it much better to install the tyvek first, and I won't do a siding job without tyvek if they want any sort of elak free guarantee. The R value of insulation board is a joke, and we only use it to smooth the wall. As for condensation, I've never had a problem with this, as I'd think the Tyvek would keep it from getting inside the house. That's what the Tyvek is for. If you've ever taken vinyl siding off a house the day after a good rain it's all wet back there anyways, which is why we insist on tyvek. Vinyl siding is not water proof, is not intended to be water proof, and I don't know a siding manufacturer that claims it to be anything more than a cladding.

Jer · 02-09-2009, 05:36 PM

The biggest benefit of the 1/4" foam board is as a wall straightener.
If Tyvek is used with this product it should be installed directly behind the siding.
As stated above remove the original barrier.

Patrick · 02-09-2009, 06:23 PM

GET RID of that tar paper!!!!!!!!!!!!!!!!!! If it ever gets wet back there, freak storm, or freak ice damn, you will have black streaks down your new vinyl

tcholdren · 02-09-2009, 07:57 PM

as mentioned before the condensation will not go back thru the wrap, but the moisture will stay between the wrap and foam board if it is applied behind the foam.

enforcer · 02-09-2009, 10:09 PM

i have NEVER put tyvek over insulation board. we always tyvek first then use insulation. but for gods sake,get rid of the tar paper and don't look back!

tcholdren · 02-10-2009, 09:37 AM

Inslation board first then house wrap over! if your installing it the other way your asking for prob!!! condensation will be trapped behind foam board! we do this all the time just button cap house wrap. if you insist on house wrap behind the foam you must use ply wood fur strips to let condensation drain out. for those who dont believe me read up on how house wrap works!!

JonM · 02-10-2009, 01:56 PM

Seems like a 50/50 split in this thread....anyone ever asked the manufacture what they recommend?

PittTrack · 02-10-2009, 02:13 PM

Quote:

Originally Posted by tcholdren

Inslation board first then house wrap over! if your installing it the other way your asking for prob!!! condensation will be trapped behind foam board! we do this all the time just button cap house wrap. if you insist on house wrap behind the foam you must use ply wood fur strips to let condensation drain out. for those who dont believe me read up on how house wrap works!!

I went to the Dupont website and found this:
Tyvek DrainWrap - Engineered with vertical grooves to provide enhanced drainage behind claddings such as primed wood, fiber cement siding and foam board.

After reading that I am guessing that it is best to either

A) Insulate 1/4 board (taping seams) then tyvek (taping seams)
OR
B) Use the DrainWrap (taping seams) then put the 1/4 board on (taping seams).

After making some calls it costs ~$125 for a 9x100' roll of the normal wrap and the Drainwrap costs ~$230 for a 9'x125' roll. I'm thinking of less headaches and just removing the existing wrap and then putting Tyvek (regular product) on and then siding over that (no 1/4 board)

SLSTech · 02-10-2009, 03:40 PM

Quote:

Originally Posted by JonM

Seems like a 50/50 split in this thread....anyone ever asked the manufacture what they recommend?

It is kinda of interesting & frustrating

No where on any of the manufacturers sites state it should be on one side or the other. Tyvek even had a part about installing the house wrap before the sheathing and how that was okay - they did state that is only good for air infiltration only in that case.

I did notice a case study on Tyvek's site where someone had installed another house wrap before the insulation & that was shot down but the details are sketchy on this one.

I guess the next time I talk to a Tyvek rep I will have to ask. My personal opinion & every job I have seen the insulation is installed on top of the house wrap. No matter where the house wrap is at - as soon as the moisture hits the foam board it shouldn't get any further. Seeing the house wrap allows vapor to pass through there should not be a mold issue based on its location.

If the moisture is coming from inside the house, I would say you are screwed if you are using the insulation & I would rather have mold growing between the insulation & house wrap than on the plywood or OSB. From the exterior I say the point is mute - whichever is on top should not allow rain / moisture to pass through

72chevy4x4 · 02-10-2009, 06:48 PM

if the insulation board (you're looking at fanfold) won't allow air/water vapor through and it's taped, what then is the point of tyvek? seems if humidity is on the inside of the structure, goes through the sheathing, hits the tyvek and stops but no air is passing regardless of if being on the front or back of the fanfold.

for those of you using 1/2" or 3/4" reflective foamboard, besides taping, do you use housewrap?

SLSTech · 02-10-2009, 07:17 PM

Quote:

Originally Posted by 72chevy4x4

if the insulation board (you're looking at fanfold) won't allow air/water vapor through and it's taped, what then is the point of tyvek? seems if humidity is on the inside of the structure, goes through the sheathing, hits the tyvek and stops but no air is passing regardless of if being on the front or back of the fanfold.

for those of you using 1/2" or 3/4" reflective foamboard, besides taping, do you use housewrap?

Good question - usually we put the Tyvek up for protection & if they want the fanfold installed it goes up as there installing the vinyl which is later in the process.

Now as for leaving the Tyvek off altogether (assuming they are installing vinyl the same day the walls go up) - I would be leery of it. How many times have you seen a properly taped & detailed install of the foam? I haven't yet

maceycon · 02-10-2009, 07:37 PM

I have never heard of putting anything under or over, maybe you guys are using the wrong fanfold insulation try GreenGuard or Polar wrap. That is what I have always used and I tape the joints.

I just added these intructions. Nothing over or under!

http://greenguard.pactiv.com/product...tion-guide.pdf

tom m · 02-11-2009, 12:30 PM

I'll chime in, this topic has been raised many times here. I always Tyvek first then insulate for pure simplicity and ease of installation. Staple guns are faster than hand nails any day. However, one time I was requested by a very anal homeowner that I install the tyvek over the foam. He swore by it.
First off Tyvek will repel liquid water, its primary purpose is an air barrier. There are seams and gaps in sheathing. A side benefit is a temporary water shield during construction. I would also say that a good foam board that is taped serves the same purpose as a housewrap and may even be redundant using both materials. I personally have no issue just doing both.
In any case moisture from condensation can pass through the tyvek. It is permeable. Another words bulk liquid rain will run off, but if you pulled off tyvek after a rain storm you would find the sun drove some moisture through. Moisture can come from both sides of a wall so thats why it needs to be permeable.
Now foil faced foam is not permable at all especially if the seams are taped now your asking for a problem. 1/4"-or 3/8" Fan fold is garbage, please lets not call it anything other than furring. A ridgid board foam like DOW, Foamular or green guard are all semi permable so they allow a small amount of moisture through. It wont kill you. You know you get the stuff delivered to the job and its all stacked up, then it rains the top few boards are a little damp the rest are bone dry.

This is obvious when you have a plank siding installed over tyvek. The outside gets painted or stained. A water leak from poor details gets behind the wall and is trapped. The paint will start peeling off the siding or go in the wall. If you pull the siding you will see line in the wrap where every plank was. Here you need furring strips for air. I would say all siding is better with a rain screen furring gap. Its just more time and money.
Vinyl is extremely forgiving because it has air spaces that stand off the wall and any water that does get in weeps out.

BlackHatch · 02-11-2009, 04:15 PM

In order for insulation to really do its job, it needs to be in direct contact with what it is insulating. That being said, the foam should be put on first and left untaped.

The permeability of some of the EPS is so low that you could create moisture issues in the walls if you tape and vapor tightened up the home too much.

I would leave the seams of the foam untaped and wrap Tyvek/housewrap over that.

spiral · 02-11-2009, 08:33 PM

Do not leave an air gap between the Tyvek and the siding!
This only reduces moisture accumulation and contributes to the longevity of the structure. Do you want the house to last forever?

Spiral