Breather Membranes
Breathable felt does exactly that, it allows the roof/roofing timbers to breath and allows moisture through to be dispersed in the outside air. Using non breathable felt (or polythenes) here would keep the moisture in which would turn to condensation when the weather cools (night time) and over time would promote the growth of moulds and be generally unhealthy. An average house produces 14 litres of moisture a day yet air leakage is a major contributor to heat loss. Energy saving, waterproof and airtight - WEB UV breather membranes allow moisture to escape and prevent air leakage.