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Liquid Applied vs. Sheet WRB

Hello Again!

I am trying to decide on the best weather barrier to use on my house, and would like to hear some opinions on liquid applied WRBs. I am looking at Henry Air-Bloc, for example. I am inclined to think that a liquid applied weather barrier would be more effective than a housewrap like Tyvek, but can't seem to find confirmation one way or the other.

I am hoping to use this external layer as my primary air barrier, so it is critical that it be as effective as possible.

I have looked at pricing for liquid applied vs. wraps, and it seems to be a huge difference - a multiple of around 5x the cost for liquid applied vs. wrap. Is this accurate, or did I just find some bad data online? Further, is the extra cost for a liquid applied WRB worth it? Are they easier to get right, more effective, more durable, etc? Any and all thoughts would be appreciated!

Thanks.

Asked by Stephen Youngquist
Posted Tue, 07/22/2014 - 05:59

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2 Answers

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1.
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Stephen,
Yes, liquid-applied WRBs cost significantly more than conventional WRBs.

Yes, a liquid-applied WRB is an effective air barrier.

I have heard only positive reports from builders who have used liquid-applied WRBs.

Q. "Is the extra cost for a liquid-applied WRB worth it?"

A. Only you can decide that.

If your WRB is detailed properly, and is properly integrated with your flashing, there is no reason why asphalt felt or plastic housewrap won't work just fine. And a liquid-applied WRB is just one type of air barrier; if you want, you can choose a different approach to airtightness (for example, using Zip Sheathing or taped plywood sheathing).

Answered by Martin Holladay, GBA Advisor
Posted Tue, 07/22/2014 - 06:16
Edited Tue, 07/22/2014 - 06:19.

2.
Helpful? 1

Stephen,

I just built a house and used a LAWB. True, it is way more money (5x sounds about right.) It is also way more work (again, maybe 5x). However, I went with this option because my particular wall assembly is inherently risky from a moisture standpoint (SIPs and masonry... long story.) I relied on the advice of Martin and Dana and others on this site, who guided me through understanding the various issues involved. The LAWB seems to address all the problems that can plague conventional sheet WRB. The system integrates beautifully with all rough openings and penetration flashings. There are no tapes or seams or fasteners or tears or stearates.

I agree with Martin: sheet WRBs can be perfectly adequate. But if you need the extra assurance of a space age WRB, go with liquid.

I used the STO system. Learning curve on that--they typically only serve commercial builders so there's not much out there to help the residential guy. As I applied STO's Emerald product, everyone passing by asked why I was painting my house green before putting on any trim. One guy asked, "is that what they call green building?"

Answered by Andy Chappell-Dick
Posted Tue, 07/22/2014 - 18:48

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