Thermal conductivity of wool and wool-hemp insulation

Measurements have been obtained for the thermal resistance of sheep-wool insulation and wool–hemp mixtures, both in the form of bonded insulation batts, using a calibrated guarded hot-box. The density was 9.6–25.9 kg m−3 for the wool and 9.9–18.1 kg m−3 for the wool–hemp mixtures. The measurements were made at a mean sample temperature of 13.3°C using a calibrated guarded hot-box. The estimated uncertainly in the resistance measurements was of the order of ±7%. The thermal conductivity of the samples, derived from the thermal resistance measurements on the basis of the measured thickness, was well correlated with the density, although the variation with density was larger than that obtained in previous studies. The conductivity of the wool–hemp samples was not significantly different from that of the wool samples at the same density. Moisture uptake produced an increase of less than 5% in the conductivity of the bonded wool insulation for an increase in absorbed moisture content of 20%. The thermal resistance was 1.6% lower on average for samples oriented in the horizontal plane rather than the vertical plane, but this difference is not significant. Copyright © 2005 John Wiley & Sons, Ltd.