The function of a vapor barrier is to retard the migration of water vapor. Where it is located in an assembly and its permeability is a function of climate, the characteristics of the materials that comprise the assembly and the interior conditions.

Vapor barriers, typically a polyethylene plastic sheeting (which is a thermoplastic and we can weld it!).  

The function of a vapor barrier is to retard the migration of water vapor. Where it is located in an assembly and its permeability is a function of climate, the characteristics of the materials that comprise the assembly and the interior conditions.

Vapor barriers, typically a polyethylene plastic sheeting (which is a thermoplastic and we can weld it!).