Building Green on Green

Tremco Commercial Sealants & Waterproofing has successfully built and tested a stucco wall in controlled “real world” conditions for air and water resistance that not only meets but exceeds one of the most stringent building codes in the United States.

Tremco’s wall assembly passed the test with no water leaks, making Tremco’s stucco solution the first in the industry to comply with the 2007 California Building Code, Chapter 14 for Exterior Walls. Prior to Tremco’s testing at its Sustainable Building Solutions Test Facility in Cleveland, no air barrier manufacturer had tested and documented that their products could comply with this code, which requires the wall assembly to pass an extended two-hour water exposure test in accordance with ASTM E331 under 6.24 psf differential pressure (normal test is run at 2.86 psf for 15 minutes).

Tremco’s testing proved its water- and air-leakage performance exceeded industry standards on a full assembly wall including the most challenging of connections and the most challenging façades. Penetrations on the wall included a rough opening with an aluminum fixed window, an HVAC duct, a PVC pipe and an octagonal junction box, per ASTM E 2357. The wall incorporated a horizontal “drift joint” near the top.

One of the challenges was making the wall waterproof but vapor-permeable to avoid trapping moisture within the wall. That’s where the ExoAir® 230 Fluid-Applied Vapor-Permeable Air Barrier Membrane came in.

The assembly began with the ExoAir® 230 membrane to keep water out, yet remain permeable to the passage of water vapor. A storefront system was then installed with Tremco’s Proglaze® ETA Engineered Transition Assembly System 1 and System 2 Molded Corners to provide a secure connection. Next, in an effort to accommodate the lateral movement during seismic or high-wind events, a drift joint was built into the wall assembly. Proglaze ETA Connections and Molded Corners with Spectrem®1 Silicone Sealant were used to detail the connections. The air barrier assembly was then pre-tested before the stucco lath and J-channel components were applied. After pre-testing, the heavy three-coat stucco cladding was applied. The wall assembly was then tested in accordance with ASTM E331-Standard Test Method for Water Penetration of Exterior Windows, Skylights, Doors and Curtain Walls by Uniform Static Air Pressure Difference.

Tremco was able to prove its success thanks to its Sustainable Building Solutions Test Facility, a state-of-the-art, fully automated facility designed for controlled testing of air and moisture infiltration/exfiltration in air barrier systems and building enclosures. The results of the test have been verified by Architectural Testing Inc. of Springdale, PA.

The passage of this test is critical because stucco claddings, common in seismic-prone California and the West Coast, face even greater challenges when builders place seismic-drift joints across the head of the window or wall system. Stucco systems are not immune to water penetration, so it is critical to maintain the integrity and weather-resistance of the exterior wall envelope. This means a continuous waterproof drainage plane must protect the structure, while accommodating the forces of nature.

Stucco facades consist of Portland cement plaster, metal lath and a water-resistant barrier (WRB), which serves as the drainage plane behind the outer cladding of the stucco. Typical building paper properly shingled as a backup has been shown not to adequately perform under new building code requirements. Fasteners used in mounting the plaster’s casing bead (J-molding) and metal lath penetrate the building paper and may allow air/moisture access while not providing an acceptable connection for the window or wall system. The ExoAir 230’s self-gasketing capability maintains a seal after penetration.

For more about the test facility, click here.

The test report is available at http://www.tremcosealants.com/testfacility/downloads/Stucco_E331-E2357_report.pdf