Tolerance for Moisture Intrusion is a Challenge in Vancouver
Earlier this week I traveled to Vancouver, British Columbia, Canada to present the workshop on Mold and Moisture Control in buildings at the final [Be Certain] event. It has been fascinating to present these workshops in different Northern climates and creating simulations to address the specific challenges faced in these areas of North America.
Previously, I blogged about polyethylene in Calgary, Alberta, Canada and the challenges faced in controlling moisture because of the use of exterior insulation. In preparation for my Vancouver workshop, I re-ran the modeling for Vancouver and the results were very interesting.
Polyamide films, like MemBrain™ because it is a breathable vapor retarder can provide additional tolerance for moisture intrusion in many climates, but in extreme climates like Vancouver there is almost no way to survive water intrusion.
In such climates, the best course is to build into the design redundant drainage planes and flash, flash, flash. Expect water to pass your principle line of defense and stop it with a secondary line of defense which will evacuate the intruding moisture to the exterior environment. This would be like a window rough opening being completely wrapped prior to window installation and this rough opening flashing draining water out and onto the face of a water resistive barrier (WRB) which leads to an egress at the base of the wall system.
While there is so much we know about moisture management, there is always more to learn and our thinking must be comprehensive. If we don’t learn from the past, our attempts to build air-tight and moisture-tight buildings will leave us looking more like Wile E. Coyote grasping for the next solution. I am not comfortable with that. Thoughts?
Lucas Hamilton is Manager, Building Science Applications for CertainTeed Corporation