Air and water resistive barrier membranes applied to the exterior of sheathings are a popular air and water management strategy for wood and steel framed wall systems. Placement of the primary air barrier system on the exterior side of framed walls simplifies air barrier detailing and also combines with the need for water control at this location. Many of these wall systems also incorporate exterior insulation outboard of the sheathing and AB/WRB in order to meet project energy code or more stringent thermal performance targets. Cladding attachments for assemblies with and without exterior insulation may include clips, ties, girts, etc. that penetrate the AB/WRB with thousands of screw or nail fasteners. Laboratory testing experience coupled with forensic evidence suggests that with enough water present at the WRB with sufficient pressures, fasteners through the AB/WRB may leak water and can impact airtightness – hence the need for new test standards and develop classification of AB/WRB membranes, sealing methods for low-rise to high-rise building applications. The authors have performed extensive research, laboratory testing, field testing and forensic investigations over the past decade or so specifically related to this issue within a wide range of membranes and different cladding attachments and fasteners. This presentation will cover an overview of the current issues, results of laboratory testing evaluating different membrane and fastener combinations including self-sealing ability. This guidance will help manufacturers and practitioners better understand the risks of different details and solutions that can be implemented to improve the long-term air and watertightness of exterior air and water restive barriers.
- Discuss risks of fasteners through air and water resistive barriers applied to the exterior of sheathing.
- Describe potential solutions for sealing of fasteners through air and water resistive barriers.
- Review forensic and laboratory testing of air and water testing of various fasteners through different AB/WRB membranes.
- Construct wall assemblies that do not leak air or water through fasteners penetrating the AB/WRB.
Graham Finch, Dipl.T, MASc, P.Eng
RDH Building Science
Graham Finch, MASc, P.Eng is a Principal and Senior Building Science Specialist with RDH Building Science. Graham works across a wide spectrum of RDH’s core service areas and is directly involved with building enclosure consulting, existing building investigation work, and research related to building materials and building enclosures across North America. Graham regularly works with building product manufacturers and other clients on product research and development, performance monitoring, forensic investigations, and field testing. He also works closely with architects and developers to support the design of high-performance building enclosures and façade systems.