Peter Yost runs Technical Services for BuildingGreen, Inc. and is Technical Director for GreenBuildingAdvisor.com. He has been building, researching, teaching, writing, and consulting on high-performance homes for nearly 30 years. At BuildingEnergy Boston, he’s speaking at a pre-conference workshop on Building Science Puzzles, and he’s joining Dave Gauthier for a session called Sticky Business: The truth about tapes and what it means for your enclosure. In the latter, he’ll report on his testing of pressure-sensitive tapes—the ones we rely on to waterproof and air seal our buildings—at what he calls his “Wingnut Test Facility.”
Ireton: I realize there’s not much to do for entertainment up in Brattleboro, but testing tapes?
Yost: Well, the cable went out and the brewpub was closed…Seriously, though, I was teaching at a conference a few years back, arguing that a high-performance house should last 150 years, and a builder asked me how long the adhesive on pressure-sensitive tapes would last. I had no idea.
Ireton: Yeah, but why test them? Isn’t it enough to know that they meet the ASTM standard?
Yost: The ASTM standards are silly. I think John Straube was the first to suggest that ASTM stands for Another Stupid Test Method. In this case, the test doesn’t reflect what happens on a job site. We want to know if the tapes will stick to OSB on a cold day. The ASTM standard requires that they stick to polished, acid-washed stainless steel. Know any builders who sheathe their buildings with stainless steel?
Ireton: Hey, I’m asking the questions here. So how do you test the tapes?
Yost: We test them in an unheated shed, so they’re exposed to temperature and humidity swings, but not to wind or UV rays.
Ireton: But most houses in Vermont never have siding, so shouldn’t you test UV and wind resistance, too?
Yost: You’re thinking of New Hampshire.
Ireton: Okay, then what substrates are you testing these tapes on?
Yost: We figure that rough OSB is the toughest challenge, so we’re using that. But we’re also testing the tapes on aluminum and vinyl window flanges and on housewraps. And we’re assuming that the tapes are installed under lousy conditions or that conditions get lousy over time, so we’ll wet the tapes, then rewet them. We’ll hang weights on them. Our rigor isn’t in the systematic nature of our testing—consider the source, we’re just a couple of guys throwing shit at the wall to see what sticks—we’re all about pushing the conditions that the tapes are subjected to.
Ireton: Is anybody else doing this kind of testing?
Yost: The manufacturers do their own propriety testing, but they don’t share the results. Nobody is independently testing these tapes under real-world conditions. We’ll stop as soon as somebody does.
Ireton: Okay, so what have you learned?
Yost: There are three common types of tape: modified bitumen, butyl and acrylic. The modified bitumen tapes don’t stick. Butyl tapes stick sometimes, and acrylic tapes perform the best. But even among the acrylics, there are differences.
Ireton: You’re killing me here. I still get confused between EPS and XPS. Now you want me to learn about bitumen, butyl and acrylic? Can’t you just give me one tape that I can use for everything?
Yost: Well, we have narrowed it down to three acrylic tapes—two made in Europe and one in the U.S.—and of those three, one of them is kicking ass.
Ireton: That’s great. Which one is it?
Yost: You’ll have to come to the conference to find out.
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