Review of moisture behavior and thermal performance of polystyrene insulation in building applications

Expanded polystyrene (EPS) and extruded polystyrene (XPS) are insulation materials used in thermal insulation systems for building envelopes, below-grade foundations, and roofs. There are approximately 56 test reports and research papers that have been identified on the specific topic about the moisture behavior and degradation of thermal performance of XPS and EPS in building applications. However, without critical review on this data, such large set of data collection can barely be used due to the controversies and inconsistences existed in the current form. This paper focuses on addressing this challenge by introducing two new parameters “SVR/Density” and “dPP/Density” during the analysis of the moisture behavior and thermal performance of polystyrene thermal insulation tested with various properties and conditions. With better interpreting on the data, the impacts of measuring techniques, test conditions, material density and insulation mean temperature on the relevant test results (moisture content and thermal conductivity ratio - TCR) are studied and clarified. According to the analysis on the appropriateness and applicability of the reported values, correlations are proposed on the variation of TCR versus moisture content and with density effect also taken into consideration. The correlations match the experimental data within the acceptable ranges.