Are “control layers” in home building confusing you? Do you know that vapor barriers are not air barriers? Are you clear that drainage planes are not vapor barriers? Despite the differences in application and purpose, the term “vapor barrier” seems to have become the blanket term for all three layers. The key is to know what you really need to control. Is water or water vapor your problem? Often contractors need a drainage plane or the water-resistive barrier (WRB) rather than a vapor layer. Take a close look at descriptions of control layer materials, insulation performance, and “housewrap” capability as you plan projects.
Read the full article here: Understanding Air Barriers, Vapor Barriers, and Drainage Planes | GreenBuildingAdvisor.com