Two-layer active membrane with variable vapour permeability, made of nonwoven polypropylene and copolymer of polyethylene functional film. In winter, when the temperature in the building is higher than surroundings and relative humidity of air is low, the vapour stream passes from the inside to the outside. Under such conditions the film pores are closed and the product shows a vapour barrier propertiesand prevents humidity from condensing in the partition. In summer, steam flows through the opposite direction – from the outside to the inside and the humidity is relatively high. Film remains open and vapour permeable, providing evaporation of moisture from partition.