| 摘要 |
The material (12,14) is particularly for a heat-insulated roof, having two or more parallel portions (24,26,28,30,32,34). A first portion (24-30) has low resistance to water-vapour and a second one (32,34) a high resistance to it, so as to form a vapour barrier. The material forms a single layer, and is resistant to draught air, the first portion being open to allow vapour diffusion, so that this can escape through it. Alternate portions with low and high resistance can be provided, the first ones having a resistance equivalent to a layer of air of 0.1 mm thickness or less, while that of the second ones is equivalent to one of 2 mm or more. The portions can extend in the lengthwise or transverse direction the material, the minimum width of the first and second portions being respectively 18 and 40 cm.
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