Hurricane in a Bottle: Testing Building Assemblies for Moisture Resistance

State-of-the-art testing chambers show that liquid-applied barriers outperform more typical weather barriers comprised of flashing, tape, and membranes.

BEA's building assembly test chamber in Clackamas, Oregon.Photo Credit: Alex Wilson

When I was in Portland, Oregon for the 2014 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.

Prosoco, a leading manufacturer of liquid-applied membranes developed the Clackamas test facility with partner company Building Envelope Innovations (BEI).

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.

With the large chamber we 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.

Tom Schneider of Building Envelope Innovations explaining operation of the large test chamber.Photo Credit: Alex Wilson

The operator can turn a few dials and simulate 150 mph wind and driving rain—wreaking havoc on the wall assembly constituents.

Prosoco company president David Boyer 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.

Prosoco’s interest 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?

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 and specialized building tapes.

Manometers and other gauges on the test chamber.Photo Credit: Alex Wilson

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.

The smaller test chamber used for measuring moisture diffusion through different materials.Photo Credit: Alex Wilson

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.

For related information, see BuildingGreen's course on high-performance building assemblies, as well as our EBN feature, Verifying Performance with Building Enclosure Commissioning.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.