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 stuccoover building paper. The data presented is a subset of experimental data from a multiphase, multiyear research project at theVancouverField ExposureTestFacility in Coquitlam, British Columbia, Canada.The analysis includes results fromnormal indooroperating conditions in a high stress exterior moisture environment (typical of thePacific Northwest climate) and under intentionalcontrolled liquid-water wettings to the interior and exterior of the sheathing. There were no measured or observed moisturerelateddurability concerns relating to the wood structural sheathing when 38mm(1.5 in.) of low vapor permeance exterior insulationwas installed.

Presented at Thermal Performance of Exterior Envelopes of Whole Buildings XII, December 2013