Testing building assemblies for moisture resistance
When I was in Portland, Oregon, the week-before-last for the Living Future Conference, I had an opportunity to visit a facility in nearby Clackamas where building assemblies and components can be tested for water intrusion and water vapor penetration.
One of the high points of being a researcher and writer is the opportunity to visit really cool manufacturing and research facilities, so I usually jump at the opportunity to visit something new. I wasn’t disappointed on my recent trip.
PROSOCO, a leading manufacturer of liquid-applied membranes (think spray-on Tyvek, flashing, and tape), developed the Clackamas test facility with partner company Building Envelope Innovations (BEI). PROSOCO was at the Living Future conference because of the company’s commitment to sustainability and transparency in building products, and company president David Boyer and sustainability director Dwayne Fuhlhage invited a number of us out to Clackamas to learn how they test for moisture resistance.
A Cat 5 hurricane
in a closed chamber
At the Clackamas test facility Building Envelope Analysis (BEA) -- a joint venture between PROSOCO and BEI -- has two specialized test chambers that can be used to simulate weather conditions as well as more insidious humidity conditions that can drive moisture into wall assemblies or damage building components like insulation and sheathing.
In the large chamber I, along with a half-dozen other Living Future conference attendees watched as the submarine-like glass doors were closed and the fury of wind and driving rain were cranked up on the controls. We could see on manometers just how much pressure the wall assembly was having to endure, and we could watch high-pressure nozzles spraying high-velocity streams of water at the assembly.
The operator can turn a few dials and simulate 150 mph wind and driving rain -- wreaking havoc on the wall assembly constituents.
David and BEI director of operations Tom Schneider explained how the test chamber can easily be configured to test everything from plywood sheathing and flashing systems, to windows and weather-barrier tapes.
When we visited, a high-tech, European window that had been submitted by a local Passive House builder for testing was blocked off, because it had failed so miserably that we would have had water all over the place if it hadn’t been sealed off.
in all this testing
We didn’t get into too much detail about building the test chambers, but it appeared that hundreds of thousands of dollars had gone into designing and fabricating them. Why would PROSOCO and BEI go to all this effort and expense?
Because BEI developed and PROSOCO manufacturers liquid-applied membranes for building assemblies, and the companies want to show off how much better they perform than the far-more-common assemblage of weather-resistive barriers (like Tyvek or Typar) and specialized building tapes, such as those made by 3M, Dow Chemical, Zip, SIGA, Pro Clima (the latter of which we used on our house).
The bottom line is that the liquid-applied weather barriers, such as PROSOCO’s R-Guard Cat 5 Air and Water-Resistive Barrier, do a lot better than the more common taped membrane systems. While one can question how accurately the test chamber simulates real conditions, the demonstration was compelling.
In addition to the large test chamber for testing whole wall assemblies and components, there was also a smaller chamber used for testing the permeability (or vapor diffusion) of specific materials -- like plywood and weather-resistive barriers.
With this discussion, I was fascinated to learn that the standard methods we use to measure the permeability of different materials to water vapor are grossly flawed. David explained that the permeability of a material that has a listed perm rating (based on standardized ASTM test methods) of 36 may drop to a perm rating of only 2 when that material gets damp from high humidity.
PROSOCO and BEI have even more sophisticated test chambers in Florida and Kansas. In addition to testing the effects of wind and wind-driven rain, the Florida facility, which I’m hoping to visit sometime, can test resistance to sudden flood or tidal surges of three to four feet.
With growing focus on resilience and adaptation to climate change, dealing with storm surges in low-lying coastal areas will become more and more important.
Alex Wilson is the founder of BuildingGreen, Inc. and the Resilient Design Institute (www.resilientdesign.org), both based in Brattleboro. Send comments or suggestions for future columns to firstname.lastname@example.org.
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