Air-Sealing Tapes and Gaskets

Construction Adhesive?
by John Brooks

I remember a framer at the JLC forum who proposed using construction adhesive between sheathing and framing in addition to the mechanical fasteneners.
I think his intention was structural enhancement not air control.
He was pretty well laughed at for "overkill"

I have often wondered about the air control quality of such a strategy?
Is the bond between sheathing/construction adhesive/framing backer reliable over time?

Rollie Peschon
by John Brooks

Martin,
You mentioned Rollie in your blog.
I think he had one of THE best construction blogs I have seen.
http://imageevent.com/okoboji_images/deloreshouse;jsessionid=7iuejflor1....

Using construction adhesive to stop air leaks
by Martin Holladay, GBA Advisor

John,
As far as I know, construction adhesive is a good air-sealing product. It is certainly the most common way to seal the crack between subflooring and rim joists; without construction adhesive, this is a potential air leakage crack. (That's why it's important for construction adhesive under subfloors to be installed in a continuous ribbon rather than a series of interrupted dots -- at least at the perimeter of the floor.)

Gap Gasket
by Dan Kolbert

We've started using Cons. Tech's gap gasket in the past year. It seems to work well, and I like it both for its air sealing and also because it leaves a potential path for any leaks to make their way down to our window or door pans and escape.

recent observation about construction adhesive
by j chesnut

I was removing an old door the other day and found the familiar brown construction adhesive was used between the entire vertical length of a 1x (used as the jamb stop) and a 2x (used as the door frame). The adhesive had turned very brittle and no longer had any holding power. When I pulled the boards away from each other the adhesive shattered into shards that fell to the floor. Hard for me to judge if something that turned so brittle but still trapped in place could serve as an air sealant.

A little context - door was on south exterior wall in a cold/very cold climate so has seen large temperature extremes. The door was probably around for 20-25 years.

Owens Corning Energy Complete
by Carl Seville, GBA Advisor

OC recently introduced an insulation system that incorporates a spray-on gasket system with either loose fill or batt insulation that appears to be a good solution to the air sealing problem. The gasket is sprayed on all gaps to be air sealed. It doesn't require the same level of personal protection as typical spray foam insulation; it expands minimally and compresses easily. I haven't seen any test results on the product yet.

Gaskets and Air Tight Electrical Boxes
by Russ Hellem

We have been selling the Conservation Technologies drywall and sill gasket for quite sometime now and have had very good success with the product. We have blower door tested several projects that used the gaskets at any wood to wood connection and utilized the drywall gasket for air tight drywall. Most of these projects have very little urethane foam sprayed in them and are insulated with densepack cellulose in the walls. One of the projects tested out at .56 ACH50, and the others were at .89 ACH50, 1.1 ACH50, etc.... Another key to this is the use of the airtight electrical box and a foam gasket around the flange. We have tried both the Lessco Airtight boxes and the Air Foil boxes and have found that the Air Foil boxes are easier to install and more user friendly for the trades. Another issue we had with the Lessco box was that they tend to push out when using densepack cellulose in the wall cavities. You can see some examples of the boxes on our website @ http://energetechs.com/test-test-test/foam-sealing-products/electrical-b...

Agree re: Constr. Adhesive
by Dan Kolbert

I too would be hesitant to use construction adhesive as an air seal for the same reason. We've been using Cons. Tech's building gaskets under our walls and sills for a while and think they're a great product.

Polyether sealant for sheathing seams
by Mike Guertin

From what I understand, polyether sealants have been used for a while in commercial construction to seal joints. Polyethers have a number of advantages over other sealants commonly available to residential builders. One company - York Manufacturing - recently started promoting a few polyether sealants for home construction.
I tried a couple products, GreatSeal LT-100 and GreatSeal PE-150 to seal seams in XPS and OSB with good success. A flare shaped attachment turns the round bead into a ribbon of sealant to coat seams efficiently without need to smear by hand. The sealants gun at low temperatures - much lower than you can effectively apply any self-adhering flashing tape. And according to the literature, have very low VOC content. Of course, like any other new product, the only way we'll know how it performs long-term is to wait 30 years and pull a few walls apart.
http://www.yorkmfg.com/all_sealants.asp

Air Sealant Tapes and Gaskets
by Doug Walker

Having been in the industry as a sealant and adhesive manufacturer for over 33 years now, I feel so sorry for the residentail builder and remodeler who is trying to sort out 1) what sealant or adhesive (caulk, gasket or tape) to use and 2) what is truly "green" in this era of significant greenwashing while standards what constitutes a sustainable product are still being identified in our small but important part of the industry. If leading commercial consultants are still sorting this out due to the rapdily increasing value and need of air and vapor barriers, must be hard for the residential contractor unless he shops at the knowledgeable specialty waterprofing distributors, or does a lot of careful research. First, very little sticks to polyethylene, it's used as a bond release in many applications. What was described by Martin Hallady as a solution for the Trenco Acoustical Sealant will work equally as well with any good quality sealant. As MIke Guetin points out, polyethers (a,k.a. hybrids, STP's or modified silicones) are used in commercial work, but in fact are still a very small part of that market, newer to these aplications, so I suggest also consider a good quality silicone or urethane depending on your application. Sealing around doors and windows, and for a redundant or secondary seal when using gaskets (they take compression sets also) these will give you the best air, vapor and WATERproof seal. Without question using peel and sticks for sealing sheet membranes is the best way to go there. I get my sealants at work for free, and yet bought rolls of Grace's product when residing sections of my cedar shingled house last year. As for construction adhesives, they've come a long way, but buy the right one and install in a continuous bead as several recommended if you're looking for them to double as an air seal. Realize all of them will be stiff when cured, so won't take much movement like a sealant as the materials they're adhered to expand and contract at differrent rates. So relying on them as both a glue and an air seal will be effective only when both materials, ie the wood to wood, or wood to concrete expand and contract at the same rate and when adhesion is great to both substrates. Want to elimiate a lot of these lap, seam and connection problems, consider a liquid air and vapor barrier such as Prosoco or Sto's, fast replacing sheet membranes in critical commerical applications. Had I resided my entire home, I would have eliminated many (not all), the various peel and sticks, sheet membranes, adhesives and sealants used to upgrade the performance of my 35 year old rotting barrier wall to a modified rain screen. But if I had, guess I would never apreciate first hand what a the pain in the neck you guys go through finding and using the products we make!

peril
by Michael Blumenthal

I remember the rush in the '70s to Urea-formaldahyde insulation,carbon monoxide poisoning from wodburning stoves and to tight a seal and MOLD. Whatever the optimum solution, it's still important to insure fresh air exchanges.

Comparison to Foam
by John Cunningham

We'll be interested to see your comparison of these approaches vs going straight to spray foam. Performance, Cost, and Labor time advantages / disadvantages. We are advocates of using a single system, often open cell spray foam as a way to get the air sealing benefits rather than flash and bat or other techniques. In new builds we believe that there is a good performance and economic case for this - but would be interested to see 3rd party data. Air in a retrofit situation is another conversation as well.

Air sealing with tape, etc go
by ED GILSON

Air sealing with tape, etc go hand in hand with radiant barriers. I noticed the radiant barrier between the rafters in this graphic.
Ed Gilson Mfg rep

Two Comments/Questions
by Kohta Ueno

Great column, Martin. A few comments:

"For sealing the seams of foil-faced polyisocyanurate (for example, Thermax, Tuf-R, or Energy Shield), many builders prefer to use a foil-faced tape with an acrylic adhesive (for example, Venture 1520 or Venture 1521). Others use Dow Weathermate housewrap tape."

We've moved away from using foil tape in this application--admittedly, it wasn't Venture Tape, but off-the-shelf Home Depot foil tape. We knew it was a bad sign when the contractor said, "Yeah, it's great using this stuff... it comes right off the polyiso if you put it on wrong!" Uh oh... It also started to visibly come off the wall during construction. We ended up switching to Dow Weathermate tape, and have been pretty happy with the tack and adhesion.

"For sealing seams in crawl-space ground covers (and for sealing ground covers to concrete walls), some builders recommend the use of fiberglass mesh tape embedded in duct mastic."

Out of curiosity, why the fiberglass mesh tape? It makes sense to use it when mastic is spanning a crack, and needs some reinforcement to take the tensile loads (e.g., duct sealing across a gap). But attaching crawl space polyethylene to walls or penetrations is more of a matter of buttering both sides, and directly attaching them (e.g. plastic-to-plastic, or plastic to wall). Some pictures of my adventures with crawl space sealing here: http://www.flickr.com/photos/70684282@N00/sets/72157624663055242/

Thanks, Kohta
by Martin Holladay, GBA Advisor

Kohta,
Thanks for your comments -- good stuff!

reply to Kohta Ueno
by Todd Rheaume

Just a little FYI - when I contacted Dow to get a data sheet of their tape they referred me to Venture Tape as the manufacturer.

New Energy Star standard says no to construction adhesive
by Li Ling Young

My experience with construction adhesive is that it is a temporary measure for use while the building is going together. I'd advocate abandoning it as a sealant. EPA says construction adhesive is not to be considered a sealant.
In response to whether finicky air sealing details are more expensive than just spray foaming the house... Spray foam insulation doesn't go everywhere that air could leak. I've seen enough distessingly leaky spray foam houses to stand firmly on the side of a dedicated air barrier, apart from the insulation. Given the relative geometric simplicity of the exterior of a home compared to the interior, exterior air barrier systems like Huber Zip are looking very attractive. Get back to me in 50 years when we know how the tape is holding up.