VAPOR

• Stops or slows the diffusion of water vapor between the interior and exterior.
• Can prevent a wall cavity from suffciently drying out - requires HVAC consideration
• Should be placed on the "warm side" of the wall. (varies based on climate) to prevent condensation in an undesireable location. Sometimes this is not possible is all seasons.
• Is classified by the permeance (0.1 perms or less, between 0.1 & 1.0 perms, and greater than 1.0 perms)