Moisture Flow Drives Water Induced Problems

Originally published by the following source: Applied Building Technology GroupAugust 15, 2018

by Timothy Ahrenholz with contributions by Kirk Grundahl, P.E., Larry Wainright and Sean Shields

The hardest part of building a resilient wall is managing moisture. If water gets inside the wall, all sorts of problems arise, including mold, rust, and structural degradation, depending on the materials used. It would be simple enough if moisture was only coming from one direction: just put a water resistive barrier (WRB) layer facing that direction and be done!  But moisture comes from both sides.  In the winter, warm, moist air on the inside heads towards the cool, dry air outside, and the opposite occurs in the summer.  The most effective solution is to block moisture on one face of the wall, and promote drying through the other face.  There are plenty of resources available at continuousinsulation.org that get into the technical aspects of this approach, collected on the water vapor control topical library page

In the video below, Joe Lstiburek gives a quick overview of moisture transmission. For more information and videos please visit  continuousinsulation.org.

For additional information, please review the following articles, as well as the previous videos in this series:

Perfect Wall Articles

  1. Creating the ‘Perfect Wall’: Simplifying Water Vapor Retarder Requirements to Control Moisture
  2. Perfect Walls are Perfect, and Hybrid Walls Perfectly Good
  3. Wood Framed Wall Insulation Calculator Explained
  4. New Wall Design Calculator for Commercial Energy Code Compliance
  5. Energy Code Math Lesson: Why an R-25 Wall is Not Equal to a R-20+5ci
  6. Continuous Insulation Solves Energy Code Math Problem

Video 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
  5. Video: How Important Is Your WRB?
  6. Video: A Reliably Perfect Wall Anywhere
  7. Video: The Best Wall We Know How to Make 
  8. Video: How to Insulate with Steel Studs
  9. Video: Thermal Bridging and Steel Studs
  10. Video: Better Residential Energy Performance with Continuous Insulation
  11. Video: How to (Not) Ruin a Perfectly Good Wall
  12. Video: Tar Paper and Continuous Insulation? No Problem!
  13. Video: Do CI and WRBs Go Together?
  14. Video: Assess Your 'Perfect Wall' Using Control Layers