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.

Presented by various experts on behalf of VaproShield LLC.