Low permeance vapor barriers, once thought to improve performance, may in fact increase interior condensation and trap moisture within the wall assembly. Due to the problems with impermeable water-resistive barrier (WRB) installation many architects are now incorporating highly vapor open WRB systems in their designs. But many still believe too much permeability is bad for a wall assembly. Studies show that highly permeable WRB systems increase substrate drying, reduce the wet time of absorptive claddings allowing permeable WRB membranes to enhance the wall assembly performance. This presentation investigates the current research on vapor open systems and discusses how more permeability enhances wall assembly performance. During this presentation we will examine:
     • Water vapor transmittance
     • Water hold out vs. air tight
     • Drying capacity
     • Vapor barriers vs. vapor open

Scott D. Wood is the Senior Building Scientist at VaproShield, providing product support on manufactured materials and investigation/testing of properties for new product development. As a building scientist he provides technical support for the company's representatives, clients, and assists in the development and updating product literature. Scott is President of SWA Consulting. as an ITC certified Level III Thermographer with decades of experience performing condition monitoring and building applications using thermography. He has many publications in areas of both thermography and building science. Mr. Wood provides investigations, consulting, presentations and training in Building & Thermography Sciences. Since his creation of the course in 2003, he provides the only 4-day Building Science Thermography class for Level I and Level II that provides instruction in the use of infrared thermography in building applications.
This presentation is pending approval for 1 hour of AIA continuing education credits.