Abstract: An underroof for a sloping exterior roof and comprising a moisture-absorbing layer which on both sides comprise spaced, substantially horizontal highly diffusion-resistant strips, the diffusion-resistant strips on the top side of the moisture-absorbing layer partly overlapping the diffusion-resistant strips on the underside and being water tightly connected along their upper edges with the diffusion-resistant strips on the underside.The underroof is impermeable to water flowing along the top surface thereof but has a sufficiently high resistance to diffusion to prevent summer condensation. Furthermore, it is capable of absorbing and discharging condensate formed on its underside.

Abstract: A vapor barrier comprises two vapor-tight layers (1,2) and a water absorbing layer (3) interposed therebetween. Openings (5,6) are provided in both vapor-tight layers (1,2). The openings in one layer (1) are arranged in displaced positions relatively to the openings (6) in the other layer (2). The vapor barrier offers a high resistance to the diffusion of water vapor through the vapor barrier from one side towards the other, and enables condensed water formed on the other side of the vapor barrier to travel in the opposite direction and to be evaporated from the first mentioned side.