Column BuILDInG SCIenCeS Fiber Cement Siding 3/8 in. Spacer R-5 Continuous Insulation (Joints Taped/ Sealed to Act as a Water Control Layer) Gap Provided by “Draining” Housewrap or Vertical Tape (1/8 in. Thick) Over Housewrap or Over OSB Sheathing OSB Sheathing 2×6 Advanced Frame Wood Wall Kraft-faced Fiberglass Batt Cavity Insulation (R-20) Gypsum Board Latex Paint Figure 4 Vapor Impermeable Foam Sheathing Installed Over OSB. The issue is the ability of the OSB sheathing to dry outward through the continuous insulation. When an impermeable or low permeable insulating sheathing is used, outward drying is restricted. Moisture redistribution and buffering and some outward drying is provided with a small gap between the OSB sheathing and the impermeable or low permeable insulating sheathing by installing a “draining” housewrap or by installing vertical strips of sheathing tape over the exterior face of the OSB sheathing on 24 in. centers (i.e. over studs). The tape thickness should be limited to around 1/8 in. thick (3 mm) so that the thermal performance of the foam sheathing is negligibly affected. an impermeable or low permeable insulating sheathing is used, outward drying is restricted. We have learned from our Vancouver work (see “Parthenon, Eh!”, March 2012) that we can get effective moisture redistribution and buffering and some outward drying by providing a small gap between the OSB sheathing and the impermeable or low permeable insulating sheathing. This gap can be provided by installing a “draining” housewrap or by installing vertical strips of sheathing tape over the exterior face of the OSB sheathing on 24 in. centers (i.e. over studs) (Figure 4). The tape thickness should be limited to around 1/8 in. thick (3 mm) so that the thermal performance of the foam sheathing is negligibly affected. www.info.hotims.com/44635-80