| 摘要 |
Condensation is prevented in a space, such as a roof insulated by sheets or boards 3 of insulating material, by providing within or between at least a portion of adjacent sheets 3, or in an aperture or recess extending through a sheet 3, a region 20 of water vapour permeable material to permit escape of water vapour. Sheets 3 may be above rafters 1 as shown, and may be of rigid phenolic or urethane board. The water vapour permeable material 20 may be reticulated polyester based polyurethane open celled foam or may be a mat of fine spun polyester strands: it may be provided with a layer 22 of paper, metal foil or PVC on opposite sides thereof, bearing an adhesive layer. |
