Alireza Sookhak - Fars Regional Electric Co. Shiraz - Iran
Mohammadreza Tajdani - Fars Regional Electric Co.Shiraz - Iran

The function of a vapor barrier is to retard 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 are not typically intended to retard migration of air. That is the function of air barriers. An excellent discussion about the differences between vapor barriers and air barriers can be found in Quirrouette. [1] Incorrect use of vapor barriers is leading to an increase in moisture-related problems. Vapor barriers were originally intended to prevent assemblies from getting wet. However, they often prevent assemblies from drying. Vapor barriers installed on the interior of assemblies prevent assemblies from drying inward. This can be a problem in any air-conditioned enclosure, in any below grade space, or when a vapor barrier is also on the exterior. Additionally, this can be a problem where brick is installed over building paper and vapor permeable sheathing. In this paper we’ll try to discuss this problem and solve it that leads us to saving energy and fuel in homes.

Vapor Barrier, Climate, Migration of water vapor