The Main Goals: Prevent interior vapour from entering the assembly from the inside AND prevent exterior water / vapour from entering from the outside.

Handling water / vapour drive in an assembly needs to include a few basic elements:

• Vapour open / smart membrane layer to the interior
• Constant ventilation to regulate vapour / humidity on interior
• WRB on the exterior, in combination with an airspace
• Durable exterior finish c/w proper back-venting

Great article from Building Science Corp: bsi-061_inward_drive_c.pdf 7 MB