The KF low permeability membrane has found its application as an initial roofing layer in building with habitable as well as non-habitable loft spaces. The low permeability membrane proves to be a very effective insulation of walls in buildings of skeleton structure (wooden or metal). In buildings in which function and simple roof shapes do not require application of membranes offering high vapour permeability and, at the same time, high strength and low material costs play major role, the low vapour permeability membrane can be used.