Buildings that are designed to meet high-energy performance requirements, e.g., passive\nhouses, require well-insulated building envelopes, with increased insulation thicknesses for roof,\nwall and floor structures. We investigate whether there are differences in the efficiency of thermal\ninsulation materials at different moisture levels in the insulation and if there is a larger or smaller\nrisk of natural convection in wood-fibre based insulation than in mineral wool. The work has mainly\nbeen performed by use of laboratory measurements included permeability properties and full-scale\nmeasurements of thermal transmittance of mineral wool and wood-fibre insulated constructions.\nIn addition, calculations have been used to calculate resulting effects on the thermal performance\nof constructions. Results showed that the thermal conductivity was unaffected by moisture in the\nhygroscopic range. The air permeability was found to be approximately 50% higher for the wood-fibre\ninsulation compared to mineral wool insulation. Measurements showed that the largest U-values\nand Nusselt numbers were found for the wall configuration. Calculation of the U-value of walls\nshowed that in order to achieve the same U-value for the wood-fibre insulated wall as the mineral\nwool, it is necessary to add 20 mm insulation to the 250 mm wall and approximately 30 mm for the\n400 mm wall.
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