Mentioned in Tsongas, G. and Olson, J. (1995) "Tri state homes:.." as reference for :

The outside of the wall cavity be permeable, and much more so (at least five times) than the inside of the wall cavity, so that water vapor could escape out of the wall cavity to the outside and not accumulate and cause deterioration of the wood members.

• condensation and evaporation : prevention and solution
• wood frame houses and walls, wood structure : permeability of outer and inner layer across cavity

1. Condensation potential in high thermal performance walls -- cold winter climate
2. Light-frame wall and floor systems - analysis and performance