Just about any air barrier will perform ok under perfect conditions, if it is installed precisely following manufacturer’s instructions.
Alas, in the real world conditions are seldom perfect. Peel and stick membranes will delaminate when their adhesives dry out, high winds will rip building wraps off their staples, and fluid-applied barriers usually have to be done over again when construction delays leave them exposed to the weather for a month or two.
If you get a rainy period that keeps the OSB, Densglass or other structural wall or CMU backing damp for awhile, you can’t even install most fluid-applied or peel and stick membranes. Dampness interferes with adhesion.
If the membrane is an impermeable vapor barrier, the moisture will be trapped. The structural wall will decay when it can’t dry out. If the water in the wall can’t get to the outside, it may migrate toward the inside, giving you water stains on the living space walls, among other problems.
Air barrier installation should be simple and easy. You should be able to install it whether the surface is damp or dry. If damp, the air barrier should let the wall dry out. If dry, the air barrier should prevent the wall from getting wet, even before the cladding goes up — even in extreme weather.
And it needs stay good in the face of weather — even extreme weather — and sunlight, for months in case of construction delays.
Air barrier products and installation must meet these requirements, not because industry standards demand them — they should, but they don’t. It’s the real world that demands that common-sense level of performance.
When products and procedures don’t match up to real-world demands, one of two things can happen.
(a) you get lucky because details of construction such as overhangs may help keep water out that would’ve otherwise gotten past an air barrier that doesn’t meet real-world requirements.
(b) you put yourself in the hands of the unhappy, multi-billion dollar construction-litigation industry. The good news is — you’ll have plenty of company.
This rant was actually not the point of this blog post. It was really just to share this cool video our videographer John Young made about how quick and easy our FastFlash air and waterproof barrier is to install. It DOES meet all those real-world requirements, btw.
And yours truly has a cameo in the video as the orange-shirted helper who assists with window installation.
I begged for a speaking part, but no. Maybe in the next one.
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