An influence of temperature on thermal conductivity of loose fill insulations of natural origin

Abstract

Abstract Basing the calculations of heat losses of buildings on the constant thermal conductivity calculated for the average temperature of 10°C may be a source of calculation inaccuracies. It may lead to oversizing heating systems or the inability to achieve high efficiency of devices, e.g. heat pumps or ventilation heat exchangers. At the same time, in the summer it may turn out that the rapidly increasing thermal conductivity of thermal insulation will not protect the building against overheating. In the paper, the authors described the influence of temperature on thermal conductivity of loose fill insulations, mineral wool, cellulose, hemp fibers and flax shives. Authors measured the properties of materials under 15 and 20°C temperature differences. The highest effect of temperature was observed for hemp fibers, with up to 18% rise of conductivity in the range from 10 to 40°C with 20°C temperature difference. While 14% rise of thermal conductivity in the range 2.5 to 37.5°C with 15°C temperature difference. The lowest increase was observed in the case of flax shives, 11% and 9% rise, respectively. The measurements were supplemented by thermal simulation performed in the Delphin software. The authors are currently researching the influence of moisture on heat transport and thermal diffusion through the described materials.