Thermal performance of flat roof insulation materials: A review of temperature, moisture and aging effects

This paper presents a review of the impact of temperature, moisture, and aging on the in-service performance of commonly used insulation materials for flat roofs. Although the manufacturer-specified R-value at 24 °C mean temperature is useful for product comparison, it does not consider the various factors that affect insulation performance. The paper compiles and presents mathematical expressions for the thermal conductivity as a function of temperature and moisture content, which can be used for building energy and hygrothermal modeling. Results show that most studied insulation materials have a near-linear relationship between thermal conductivity and mean temperature, with varying sensitivity to changes in temperature and moisture content. Additionally, the severity of the micro-climatic conditions the insulation board is exposed to, rather than its service year, affects moisture uptake and thereby its thermal performance.