What are vapor barriers or weather resistive barriers and how significant are they?
As water vapor routinely moves from a volume of higher water content to one of lower water content, a low permeability barrier is often used to retard or stop this movement. A vapor barrier is intended to block or reduce water movement in the vapor phase, while a weather resistive barrier is intended to “breath” but retard water penetration (UBC ยง1402, Chapter 14, Vol 1).
