| Abstract | Air barrier systems (ABS) play an essential role in controlling the risk of condensation within wall assemblies by minimizing the infiltration and exfiltration of air through the building envelope, as specified in the National Building Code of Canada (NBC).
This research work is focused on air leakage performance of a liquid-applied silicone-based ABS. The ABS included an air-barrier membrane applied to the field of the wall, a liquid-flashing applied to concrete elements, window openings, corners and gaps, an elastomeric sealant for joints, and a prefabricated transition membrane to bridge different wall elements and large joints. This ABS was intended for application in commercial steel-frame construction.
We first report on the testing of the standalone membrane on the basis of ASTM E2178 for air permeance. The standard method requires some modification to allow for the testing of elastomeric silicone membranes. We also report on the air-leakage testing for the entire silicone system, in accordance with CAN/ULC-S742, in which testing at both 20 °C and −20 °C is required on three wall test specimens as per ASTM E1424 and ASTM E2357. In this instance, the three wall test specimens had, respectively: no penetrations; a window and 10 other penetrations; and, a junction with a concrete floor and 27 penetrations.
For acceptable performance, the NBC requires an ABS air leakage rate below 0.2 L/s•m² at an air pressure difference of 75 Pa before and after wind aging, and testing at both 20 °C and −20 °C. The air leakage test results showed that the air leakage rate of silicone ABS can be well below 0.2 L/s•m² at 75 Pa, and at least an order of magnitude better. In this paper we describe the test methods and troubleshooting necessary to characterize the materials in accordance with the standard methods. |
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