A Vapor-Open Assembly
Dan Kolbert uses a 12-in.-thick double-stud wall assembly includes two 2×4 walls separated by 5 in. of uninterrupted insulation space. They use plywood sheathing, which becomes more permeable than OSB when it gets wet; a vapor-open, fully-adhered WRB, which also provides the exterior air-sealing; and only a class III vapor retarder when combined with ventilated cladding. Drawing: Michael Gellatly - Fine Homebuilding