Technical Digest - Breathability & Mositure Vapour Permeability

When the term breathability is referred to with reference to building materials it is not concerned with air, but with water in both liquid and gas form. Breathability tends to be used to describe the passage of water vapour and there are a variety of related terms that are used to quantify breathability. Water affects everything in building from the health or decay of building fabric, through to the thermal performance of the building and to the health of occupants. Particularly as we try to increase the air-tightness, thermal performance and indoor air quality of our buildings, breathability has become a critical issue, affecting all areas both of new build and of renovation