In North America, the apparent thermal conductivity (and R-value) of building insulation materials is commonly reported at a mean temperature of 24°C (75°F) and practitioners typically assume thermal properties remain constant over the range of temperatures that are experienced in building applications. Researchers have long known and acknowledged the fact that the thermal properties of most building insulation materials change with temperature. There has been little more than academic reason to measure and report this effect. However, interest in temperature-dependent thermal performance has grown with the introduction of new materials, increasing concerns regarding energy performance, and the development of transient energy, thermal, and hygrothermal simulation software packages (e.g. Energy Plus, HEAT2, WUFI etc.) that have capacity to account for temperature-dependence. This paper considers two methods to measure, analyze, and report the temperature-dependent apparent thermal conductivity or resistance of building insulation products.
Presented at the 15th Canadian Conference on Building Science and Technology.