Trial by Fire: Water-Resistive Barriers Must Now Pass Burn Test

From D+D Online, September 2012

by Gary Henry

If you’re designing the exterior walls of a building of Type I, II, III or IV construction, 40 feet or higher, there’s a good chance it’ll have to undergo “trial by fire” — testing under NFPA (National Fire Protective Association) 285....
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Tagged categories: Air barriers; Barrier coatings; Building codes; Building Envelope; Fire; Water-resistive barrier

Comment from Gerald Curtis, (9/7/2012, 10:39 AM)

This article by Mr. Henry is a good one, well written, and informative. It does, however, make the common mistake that has appeared uncorrected in various Webinars and similar articles of NOT properly describing what Mr. Henry, and others, call a "vapor barrier". What's new... What’s new for the 2012 code is that combustible, water-resistive barriers are added to the test requirement in section 1403.5 of the code. Water-resistive barriers include air and vapor BARRIERS. (Emphasis added.) The Army Corp of Engineers' Cold Regions Research and Engineering Laboratory established MANY years ago that there is NO SUCH THING as a vapor BARRIER, and that the proper term to be used is "vapor RETARDER". For Mr. Henry and D+D Editors to allow this misinformation to propagate is inaccurate and unfortunate. The term "air barrier", in common use, and, at least for the time being, appears to be acceptable as written.

Comment from Gary Henry, (9/11/2012, 10:23 AM)

Thanks for the comment and for reading the article, Gerald. "Vapor retarders" it is! I'm guessing "barrier" is out because even the most impermeable membrane is not absolutely 100 percent vapor-proof? Thanks again for reading the story, and for the clarity.

Comment from Barry Lamm, (10/8/2012, 4:05 PM)

A recent continuing education seminar I attended refered to it as a "weather barrier." Anyway, leave it up to regulatory agencies to screw things up badly with their catch 22 situations and ways to add more costs to the public in the name of safety. What a ripoff.

Comment from Robert Lombardi, (10/9/2012, 8:57 AM)

As a long time industry veteran I have seen it all. This is just another way for EIFS manufacturers to create entry barriers for other good products and companies. It’s an old game and the code people should be aware of this tactic. Weather barriers are not only associated or used with EIFS. Some weather barrier manufacturers make an excellent performing single component product. How would they test the product under NFPA285? And where does it end? Does one test every different cladding with every different barrier? There are other less expensive tests that can be run and the results just as conclusive. Nobody wants unsafe products in the market but a full blown expensive NFPA285 test is not the way to go.

Comment from John Edgar, (10/11/2012, 9:45 AM)

Bob, Your long time experience with the EIFS industry should tell you that this test was put on the EIFS industry as an entry barrier to EIFS. The EIFS Industry did not create it but has been required to test to this level since the 1980s. Funny how so many are now getting the vapors for having to provide the same test data. This demand is not coming from the EIFS industry but from others who have tested and found some of the assemblies do not perform as well as EIFS. The barriers were established by code without any help from the EIFS industry.

Comment from Jon Edwards, (10/11/2012, 11:06 AM)

If designers / builders would use AAC [autoclaved aerated concrete] for their exterior walls this whole issue of fire resistance & testing would be moot!

Comment from Joseph Lstiburek, (10/16/2012, 8:08 AM)

Mr. Curtis, with due respect, I must disagree with you. There are vapor barriers and there are vapor retarders. The Army Corps of Engineers did no such work. A discussion of the various terms can be found at: Many years ago litigation involving a failed assembly caused ASTM to back off the term "barrier". This move by ASTM was never universally accepted and caused quite a mess. ASTM folding like a cheap suit to the concern over litigation? The legal profession crossing swords with the engineering profession? I am sure some of you are just shocked, shocked at this.....apologies to Chief Inspector Renault. The issue at the time was not physics, but the absence of a definition of terms. A definition that was testable was missing at the time of the litigation. This is no longer the case. Consider the use of the term "air barrier" and "air retarder". We have a definition for these terms and the terms are in common use. Definitions for air barrier material, air barrier assembly and air barrier enclosure exist. They can also be found at the previously referenced website. I am sure you are not proposing the same logic that some of the lawyers in that case many decades ago used to argue against the use of the term "air barrier" in favor of "air retarder"?

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