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November 17, 2011

Comments

Tyler Douglas

I am actually talking to an archetect today about a continuous liquid applied air barrier for a multifamily complex. The benefits are very great to shift from a wrap to a liquid applied simply because of the superior water protection you get with such a product.
Commercial has picked up on the need for better weather / air barriers, and the residential side is just catching up, mainly because building codes are driving the change.
I am currently installing an air barrier with a price point that the residential market in Utah can support. The main holdup for Multifamily is the cost. A commercial grade air barrier might be too expensive to be applied in that application.

B Mac

Alistair, nice piece. Just wanted to send word to those interested that Tyvek CommercialWrap and CommercialWrap D recently completed ABAA evaluation and are now listed at the ABAA website as meeting all requirements for commercial Air Barriers (materials and assemblies) and weather resistive barriers. So you're right, we are seeing the addition of performance testing requirements that do measure the effectiveness of the approach.

Alistair Jackson

Thanks B Mac. It's great to hear that there are more approved products available. I believe the ABAA listing only addresses material performance against ASTM E2178; assessing the material's resistance to air infiltration. That's an important first step, but on its own, is insufficient. Equally important are the material's ability to remain effectively sealed at seams, to resist perforating damage where it is mechanically fastened to the building, and to "tolerate" other challenges to its air-tightness during construction - such as abrasion, wind tearing and so forth.
Envelope performance testing is a major step towards better building performance, but failing the test can be an expensive headache. Quality assurance steps taken by the design and construction teams are critical to ensure successful testing at completion.

ABAA's website - www.airbarrier.org - is worth a visit. Can anyone recommend any other great resources for air barrier installation details?

Alistair Jackson

Tyler Douglas - thanks for your comment. We've had some limited experience with liquid applied products. Initial impressions suggest they are effective, but costly, as you suggest. They maybe easier to install than membrane systems, which may result in lower overall costs. Does anyone have first hand experience to share?

One other aspect of liquid applied air/weather barriers is that while they may enhance a building's durability, I suspect they also render the sheathing useless for anything except the landfill once that building finally reaches its service life.

Tyler Douglas

As for cost, the starting point for cost could be as low as $.75 per sqft installed, depending on the height and total project size. Other commercial products range from $2-$3 at least installed.

Here is the link to the application instructions for the product Envirodri I was talking about. I think the paperwork to have it on Multifamily projects will finish this year. I will keep you up to date. Liquid Applied Air barriers have to pass as an assembly, making it a superior product because of the stricter tests that are enforced. It would be a large step forward since it is less than half the installed cost of other air barriers on the market currently. It is a Vapor Permeable Product allowing water to slowly defuse through the sheathing to the outside, but restricting bulk water from entering in. The system includes detailing over every sheathing joint and flashing over windows to completely replace papers or wraps.

http://www.guaranteeddrybasements.com/fileshare/installation/TBS0564EnviroDriInstallInst.pdf

They manufacture other air barriers under Tremco commercial such as Exoair, but like I said, the price point is higher than EnviroDri.

http://www.tremcosealants.com/commercial/products/product_types.asp?type=26

As for reusability of the sheathing, That might be a minor cost compared to the energy savings one might get with a tighter building and upfront savings in HV/AC. Not to mention the savings in liability with a product that is much more durable and lasting than papers or wraps. It also helps in the energy performance since under 0mph winds to 75mph winds, there is no change on how effective it is as an air barrier.

As for experience, I've installed over 10,000 sqft of EnviroDri on smaller residential projects. The most sucessful one was in Park City Utah where I not only sealed the seal plate but also the windows to the sheathing with the reinforcing mesh, providing a monolithic seal to the window and sheathing.

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