Diffusion/Vapor Pressure
Up one levelDiffusion is the movement of heat or moisture along a concentration gradient. Although this is correct scientific definition, most people in the building industry are concerned only with water vapor diffusion, and the potential for it to cause condensation wetting during cold weather. This is a misplaced focus. Diffusion of water vapor is important, but its role in drying is the most significant, and the potential for diffusion-driven condensation during hot weather is also important.
To understood vapor diffusion and the proper use of vapor control layers like vapor barriers and vapor retarders one needs information about vapor in air, how vapor moves, and the laws of diffusion.
- Diffusion/Vapor Pressure Documents by zope — last modified 2006/02/26
