A.Joseph Lstiburek responds: The biggest factor causing moisture problems in walls is excessive indoor humidity. If your building operates at between 20% and 30% relative humidity (a comfortable level for most people), the walls should be fine with any kind of sheathing.

If indoor humidity rises above 40%, moisture in wall assemblies isn’t your only worry. Condensation on windows will probably cause trouble as well, and the mold that starts growing on cold spots can become a health problem for the home’s occupants. So your first strategy should always be to reduce indoor humidity.

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