Moisture-Related Durability ofWalls with Exterior Insulation in the Pacific Northwest

This paper compares the moisture-related performance of a wall with exterior insulation installed over oriented strand board (OSB) to the performance of a drained and ventilated wall with a 19 mm (0.75 in.) gap and a wall with direct-applied stucco over building paper. The data presented is a subset of experimental data from a multiphase, multiyear research project at the Vancouver Field ExposureTest Facility in Coquitlam, British Columbia, Canada.The analysis includes results from normal indoor operating conditions in a high stress exterior moisture environment (typical of the Pacific Northwest climate) and under intentional controlled liquid-water wettings to the interior and exterior of the sheathing. There were no measured or observed moisturerelated durability concerns relating to the wood structural sheathing when 38 mm (1.5 in.) of low vapor permeance exterior insulation was installed.