Non-breather membrane, also known as a high-resistance membrane, is a type of roofing felt that does not permit vapour through. These are specially made for “cold roof” houses, which have insulation between the rafters. In these sorts of houses, a non-breathable membrane would be impractical.
This is because in a cold roof house the loft or “roof void” is colder than the house below, rather than at a similar temperature. This is popular in places for instance with heavy snow, because it helps prevent the formation of ice dams on the edges of roofs. This is because the warm roof will melt the snow into water, which will build upon the colder edges of the roof and refreeze. Cold roofs will leave the snow in place till it melts alongside the snow on the edges of the roof.
At ERoofing, we stock high-quality non-breather membranes from brands like Cromar. Don’t forget roof ventilation is even more important in houses with non-breather membranes. You can see our selection of top felt vents here.