Thermal conductivity and specific heat capacity of insulation materials at different mean temperatures

Abstract

Thermal conductivity and heat capacity are among the most essential properties of a building insulation in calculating thermal performance which are subjected to change when exposed to temperatures variation in service. Ignoring the temperature dependency of these material properties can result in under and over estimations of buildings energy uses and the corresponding equipment sizing. To obtain more realistic conductivity values of insulation materials, in this paper, thermal conductivity tests are conducted at various mean temperatures. For the study six commonly used insulations including Cellulose fiber, Expanded Polystyrene, Extruded Polystyrene, Open Cell Spray Polyurethane, Polyisocyanurate, and Mineral Wool are considered, and their thermal conductivity are measured at seven mean temperatures ranging from 5°C to 60°C. Furthermore, their specific heat capacity are measured at nine mean temperatures ranging between 16°C and 36°C. The results showed that except Polyisocyanurate board, the thermal conductivities and specific heat capacities of all insulation materials increased linearly with rising temperature, presenting a linear regression model with correlation coefficients (R2) values between 0.96 and 0.98. The curve fitting of the Polyisocyanurate thermal conductivity measurements resulted a nonlinear regression model with R2 of 0.97. The thermal conductivity of six insulations as a function of temperature have been established.