Air Sealing Sheathing To Wood Studs
Last Post 28 Nov 2017 01:04 PM by kach22i. 14 Replies.
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kach22iUser is Offline
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23 Nov 2017 01:39 PM
Air Sealing Sheathing To Wood Studs, what do you know about it?

In several areas of the forum people have mentioned caulking the wood studs to the exterior sheathing.

However, it was unclear to me if they meant while the sheathing was going up by caulking the stud (incl. top and bottom plate and headers) face prior to mechanical attachment (nails/screws). 

Some posts suggested caulking from the backside after the sheathing was nailed to the studs, that just sounded like twice the work and caulk to me but it keeps the icky gooey caulk off the rough framer's tools and I bet they appreciate that.

I found this article on specialty products designed for such a task from the inside.

Air Sealing with sprayable caulk.

Construction adhesive applied to the stud face when attaching the sheathing just as done with floors and subflooring would make the wall stronger, but it most likely dries too hard and is not so great at gap filling.  See the 2013 thread below.

2013 thread.

Nothing in the IRC that I know of allowing or disallowing caulking stud faces.

Nothing in the American Wood Council publications, see pages 8-9.

AWC  (unknown publication date - could be old or outdated)

The battle between spray-in foam insulation and all forms of batts and or blow-in insulation comes down to air penetration issues and of course costs.

QUESTION-1: If batt (fiberglass/ mineral wool) and blow-in (fiberglass and cellulose) had the cost of sealing up the framing with caulk added to them, would they start to perform on par with spray-on foam comfort and draft wise? 

QUESTION-2: Would the costs be now more similar? 

QUESTION-3: Man hours and scheduling time lines, how altered would that become?

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EDIT-1:  I kept expandable gap filling spray foam out of this because it may intrude into the cavity too much, isn't suited for sealing up the gap between the top plate and nailer plate, and joints found around headers.  In addition products like Great Stuff cannot defy gravity and be used on the underside of window sills and the like, at least not at my current skill level.





George (Architect)
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greentreeUser is Offline
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24 Nov 2017 01:43 AM
Ive done quite a bit of this on new construction and have the benefit of owning blower doors and IR to spend some time testing my own work.

My perspective is

1. Your link of sprayable for the Owens Corning I looked into when it first came out. The problem was you had to buy their equipment and it wasnt cheap, at the time it was almost like they were trying to setup a franchise type model.

I then had talks with Knauf about using ecoSeal which I still think would be the cadillac way to go, problem is the product was expensive, if I remember right around $350 a pail 4-5 years ago, dont know the current price, and you need a decent sized Graco to push the product and spray it, it would have been $2-3k or higher sprayer, just for airsealing which might entail 1 or 2 days and I would have been doing 1-3 houses a year.

2. Caulk: a lot of polyurethanes are exterior use only and high in VOC, then you need to have a decent class rating so you dont run the risk of joint failure. Then you need cases and cases to do every stud bay, top plates, ect and even with a pneumatic or cordless caulk gun its a slow process, requires CLEAN joints so you need to do a good job vacuuming, all in all I found it to be too labor intensive for the strong possibility of joint failure in a wood frame.

3. 1 part gun foam for all of my stud bay air-sealing and poly caulk preferably on the exterior for sill plate, wall plates (under and exterior joint) 1st to second floor joints, trimmer studs ect. 1 part is done when framing is done before trades start drilling, poly on outside is done when go around the exterior and do our fill in sheathing and WRB detailng with the stick lift.

The key for me is the 1 part doing most of the heavy lifting because I can do it extermely fast and the can yields are really good which keep labor and materials down. It takes some setup but once you master speed and flow if you were to tear off the expanded bead of foam on a perpindicular joint, you can see foam material that has injected itself deep into the stud/sheathing space. If you put out too much material or go too fast the foam rolls off the side of the stud or sheathing and wont inject fully into the gap.

I also come back through prior to insulating and take care of missed trade gaps and I close off every electrical wire hole in exterior walls and exterior to interior walls with the concept that if I do have a joint failure it will contain the air leakage to that particular stud bay.

Man hours and cost will depend on experience and understanding, for me I can sell it for a good price and make good money doing it and later reap the benefits of referrals when they realized it actually was a good idea worth the money.

The result will be under 1ACH50, consistently.

To find all this out I have had drywallers come in and just hang the ceiling so I could blower door test different sealing methods and test before any air sealing was done to identify where most of the leakage comes from. Its really eye opening. ( I do attic top plates and penetrations after drywall is hung, usually before I blow attic space) most of the time I do BIBS wall insulation, but there is a real premium to that (to myself, I do that in house as well)

I think a decent batt job in air sealed cavities works pretty good. Other times Ive done BIBS in cavities less than full width and batts in full width cavities, it was definately cheaper than full BIBS but I really didnt devise a way to benchmark it with other systems and dont really have the time to do that kind of analysis though Id like too.

Any of the above in my opinion is more desireable than spray foam and for much less cost. The idea that spray foam is the premium cure all needs to go away, have seen quite a few examples of bad spray foam installations.
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24 Nov 2017 06:58 PM
Greetree, nice post.

I will look for some youtube videos on that method, now that I know what to look for.

One day perhaps you could do a video.

If a picture is worth a thousand words, a video must be worth at least a couple of thousand.

George (Architect)
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25 Nov 2017 07:32 PM
This might be an expensive or not to code question, but has anyone considered using a shiplap exterior plywood siding as an ext sheathing? Something like Georgia-Pacific's Plytanium? I'm thinking the joints could be caulked during instalation, not so much for water intrusion, but for air pressure leaks. I'd provide a link, but I'm posting this from my cell phone. Not sure if this is rated to hold metal brick ties nailed into the studs as it is half thickness at the joints because of the shiplap. And the rough sawn face could be too texture and cause friction/wear on housewraps, plus possible adhesion issues with mastic type flexible base flashings (brick veneer). Just an idea, not a suggestion at this point. Taping butt seams alone verses a shiplap and tape, the latter would have to be better and more air-tight, right? EDIT NOTE: Plytanium might only come with grooves like T-111, in that case this idea is a bust.
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26 Nov 2017 04:39 AM
Similar to gluing sub-floor to floor joists, if you can apply a good polyurethane construction adhesive such as Loctite PL Premium to the stud, bottom plate, and top plate faces prior to installing the sheathing, you could create a strong air tight barrier. It doesn't really need to remain pliable if it is stronger than the substance it is attached to and that is the case with PL Premium. And it isn't that expensive if you buy it in 28 oz tube cases (~$7/tube or $84/case of 12). But it can be quite messy if you get it on your hands or tools and if you don't clean it off before it cures, you will have to wear it off as I have not found anything that will remove cured PL Premium construction adhesive.
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26 Nov 2017 05:40 PM
If possible, use tape or gaskets. If not, my guess is that long term sealant air sealing effectiveness is, best to worst:

1) pre-applied to the faces
2) post applied high movement capability sealant done right (see here).
3) #2 done the way most people do it
4) post applied low movement capability sealant (like canned spray foam).

It's a good question about #1 - is adhesion and tensile strength more important than movement capability?

I find it interesting that Loctite PL Premium is only rated to 0F - does it get brittle below that? Perhaps better to use something like Tremco Dymonic 100 (good adhesion, strength and movement capability, -40F)
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27 Nov 2017 04:10 AM
A 28 oz tube of Pl Premium will go 86' or less with a 1/4" bead, Thats about 8' of 9' high wall, so if you need to seal 170' - 200' or more of exterior wall you have a major expense as well as a labor heavy proposition. Framing is going to slow considerably, watch a crew deck floor joists for proof, you will notice the bottleneck of the operation is laying down glue. So beyond higher material cost, you have not only the raw labor but also a lost efficiency cost that could be significant.

Modular builders will use an adhesive foam on all their exterior sheathing to give the mod strength as it goes down the highway, I think their use of foam versus a gunnable product will tell you which product is more cost effective.

On jonr's list you can forget #2, NO ONE is going to apply a tiny bondbreak to the entire perimeter of every studbay, but technically that is the correct way to create that type of joint with sealant to avoid joint failure.

If you seal between sheathing and studs you want a sealant designed for a bedding joint, like acoustical or butyl. Tremco Dynomic 100 isnt designed for bedding, I believe Tremco Dynomic FC is, still expensive as it will have similar coverage rates and labor issues as above.

I dont believe the seal needs to be perfect or even maintain integrity as long it is physically there; think of it as stuffing a rag in a hole. Really what we are doing is reducing the effective leakage area or the amount of space open from interior to exterior. Thats why I dont like the idea of tapes, if it fails the hole remains, at least with sealant, glue, or foam the hole is filled.
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27 Nov 2017 06:05 PM
Good point that costs are a significant factor in air sealing. Sealing every stud is expensive and other methods might be more cost effective.

Imagine a sealant is applied when a gap is zero and then the gap opens up to 1/8" with movement or contraction. I suggest that a good flexible tape (or gasket) would seal and a sealant is likely to leave a gap.

Tremco recommends Dymonic FC and a few others for bedding - but not their acoustical sealant. Most of their sealants are recommended for wood. So it's not clear to me what bad things would happen with a non-bedding one pre-applied between overlapping wood joints.
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27 Nov 2017 09:11 PM
For an air barrier, you don't have to seal every stud face if the sheathing is placed long side vertical and spans from bottom plate to top plate. All that is needed for air sealing is a continuous bead of adhesive/sealant around the perimeter of each piece of sheathing, i.e. 24' of bead for 4x8 sheathing or 26' for 4x9 sheathing. With this approach, one 28 oz tube of PL Premium would cover ~3 sheets of sheathing or ~12 linear feet of wall coverage. Assuming 200 linear feet of exterior wall, that equates to ~17 tubes x $7/tube = $120. Figure three or four extra tubes for around windows and doors and you are around $150. That seems pretty insignificant to me in the overall cost of constructing a home.

With that being said, a polyurethane spray foam adhesive such as GREAT STUFF PRO Wall And Floor Adhesive would probably go on faster and easier. One 26.5 oz can of this stuff provides 192' linear feet of 1/4" bead, which is about double the linear feet you get from the 28 oz tube of PL Premium, but a can of the spray foam costs about double the cost of the 28 oz adhesive tube so the overall cost is about the same. Plus you need to buy a pro style spray foam can gun which is at least double the cost of a good quality large tube caulking gun.
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28 Nov 2017 01:29 AM
Arkie,
If you are doing a diy then cost may be insignificant, but you're telling me your going to take 2 weeks off and be the glue guy with the framers? If not be prepared to pay and then wonder if they are doing a good job. Plus dealing with stud bays is the easy part, all the framing transitions, plates, ceiling plane changes, 1 story bumpouts against a 2 story, windows and doors, penetrations, ect take the most time and where the wheels fall off for most guys. Any idiot can glue the perimeter of the sheathing.

I have seen air sealing sell costs at some trade shows and seems to be anywhere from $2500 to $6000, maybe more. My house is around .6 ACH50 and my material and labor cost at $40/hr (to myself) was in the neighborhood of $1500-2000 total. My house has a complex layout, is over 4500 conditioned and over 40,000 cubic feet. My framers would not have been able to do it to the level I wanted, it takes a tremendous level of detail and thought of interactions of the assemblies, if I would have demanded that level from them it would have cost me a lot more, and they are very good experienced framers. I think most guys just dont have the interest. Because I frame with my framers or am at least onsite I can jump in and seal during framing starting with the mudsills.

And the 1/4" yield on a can of gun foam should be well over 1000' of bead. I use touch n seal, it costs me around $8 a 24 oz can (by the case) and manufacturer says 2200 lineal feet per can at 1/4". My beads are probably 1/2" wet, house will take 1 or 2 cases for everything. Ive had adhesion issues with PL Premium (and the gross odor). I noticed some squeeze out was very brittle after it set up, I could easily pick it off.

Jon, my mistake on the acoustical sealant you are correct. FWIW, Tremco has a selection matrix somewhere on their website listing 7 bedding products. Tremco FC is my favorite since you can use it on virtually anything and it guns/tools nice, just stock 1 type. Does bedding product matter over traditional off the shelf sealant? I dont know if it makes any difference, but my approach is to attempt to match product with use.

I also have never seen sheathing pull away from the studs unless maybe its not fastened correctly. Most of the sheathing gaps I encounter are due to stud width/plate width inconsistencies or out of plane.

The most frame movement probably occurs in the first year. Right after framing to a couple months after drywall is finished is the wettest stage of the building, if you get alot of movement after that I would say somethings wrong, exceptions can usually be traced back to some sort of event or oopsie.

Ceiling drywall pops seem to crop up going into the first winter cycle after drywall is done when you may get some truss movement, then you can curse the drywallers for not floating their corners. wall pops seem to show up in the first couple months after drywall is done in my experience. After that the frame is pretty static, at least no extreme movement. Ive tested my own and family members houses years apart, my latest gets tested a lot (prob 6 times this year) as Im screwing around with different things and got BPI certified so I was expanding my horizons. Cfm50 is always the same, within 5-10 cfm.

Are you guys actually actively building using any techniques or just speculating? If someone builds a better wheel I would certainly try it out.
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28 Nov 2017 01:49 AM
Oh, and Arkie, sorry to be a d bag, but a great stuff foam pro14 is what I use, $45 and as Trump would say "lasts many, many cases, sooo great," except Im actually telling the truth. My Albion 12q caulk gun, which is a standard good quality caulk gun was around $40, so the double price dispensing instrument argument doesnt work. I have used cheaper quart guns, 12.99 or more at menards, most expensive they carry, and its maddening.

No power, handle will snap off with use (Ive bought more than one when I forget a good one and they are always the same) verified sh** and for some reason their puncture wire is like 2" long so unless you want to lay down a 1" bead it doesnt reach the foil to open a tube. Then, after said wire gets a little bent and wont stay put it swings down into your hand and gives you a little scrape with every pump. So then it gets a piece of ground wire tied to it so you can puncture a tube and that scratches everything you lay it on. Hit the pressure release but product keeps coming out for 10 minutes. I am guilty of beating a cheap quart caulk gun to death with a hammer.
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28 Nov 2017 01:51 AM
I was looking something up in the code and as it happens my eye catches something else. That something else was in an older version of the residential code (2003, still looking for the current one - misplaced) Michigan's own version of the IRC by the way.

R602.10.11.2 Sheathing Attachment, adhesive attachment of wall sheathing shall not be permitted in Seismic Design Categories C, D1, and D2

Looking at the USA map on page 28, figure R301.2(2) these areas look to be well south of me, but many of you might be in those areas. That map is hard to read, bet there is a better one on-line.

Anyway the 2015 code might be different, and the 2018 code in a few years different from that. Just bringing it up because if you live out west or middle and east this could be an issue.

EDIT:  Earlier today I read an article that had three videos in it, the guy was attaching sheathing in the usual manner, flipping the wall over caulking all studs with a gun (no paper tube) and using a bondo spreader to press it into the joints, and then tilting up the walls.  He also had these plywood return bucks, bottom plate sloped 10 degrees.  Quality work, very slow and labor intensive.  He was in Oregon I believe. 



George (Architect)
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28 Nov 2017 02:00 AM
Double Post


George (Architect)
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28 Nov 2017 05:06 AM
If by no paper tube you mean the gun looked like a solid metal tube that would be a sausage gun which is how a lot of the commercial or higher end product comes packaged.

Most likely a fluid applied membrane, dupont has tyvek fluid applied in tubes. Some other brands are prosoco, sto, carlisle, tremco, henry, dow, basf, if you want to check their systems out. Im sure there's more. Typically spread the flashing component, the air/water barrier component is usually spray or roll to certain mill thickness. Some brands are one coat, some/all have joint tape and other stuff you have to do. Expensive but maybe competitive or on par with eco seal or energy complete, thats a guess, never priced it.

If they could do an eco seal type product that used a smaller sprayer and bucket price came down to foundation bucket prices ($100) that would be game over.
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28 Nov 2017 01:04 PM
Posted By greentree on 28 Nov 2017 05:06 AM
If by no paper tube you mean the gun looked like a solid metal tube that would be a sausage gun .....................

Yes, that's what he called it.

I found the article with the videos.

Hammer and Hand - via Green Building Advisor

Aside Request:  if anyone has articles or links with good head/lintel and jamb details featuring thermally broken paths when returning brick/stone/masonry veneer, please post them. 

Not much use going through all the work of sealing up the building skin only to have all the door and window openings bridge energy and leak like crazy.

I'll consider brake metal or even cellular PVC opening returns, but favor returning the 4" brick veneer to the window/door frame because it expresses the depth of the material and shows that it's not a thin-set material.
George (Architect)
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