Video: How Important Is Your WRB?

Originally published by the following source: Applied Building Technology GroupJanuary 16, 2019
by Timothy Ahrenholz


As you design a building envelope, it can be easy to focus on getting the insulation right.  After all, the International Building Code goes to great lengths to require specific R-values and U-factors.  And while the thermal control layer is certainly important, the building code is less specific about the other major control layers: the water resistive barrier (WRB), the air barrier, and the vapor control layer.  Water, air, and vapor are harder to quantify than heat which is why the code spends less time discussing them.  But if your wall fails to control them, all the insulation in the world won’t help.

Fortunately, the folks at have compiled many helpful, free resources to give you guidance where the code is silent.  Visit the topical library pages for WRBs, air barriers, water vapor control, and thermal insulation for articles, research reports, step-by-step installation guides, and more.

Also, take a look at this quick video, part of a series where Joe Lstiburek, Ph.D., P.Eng, explores effective building envelope design:



Previous articles in this series

  1. Fear Building Envelopes No More with This Website & Videos
  2. Thermodynamics Simplified Heat Flows from Warm to Cold
  3. Moisture Flow Drives Water Induced Problems
  4. Video: How the 'Perfect Wall' Solves Environmental Diversity