Below-Ground Performance of Rigid Polystyrene Foam Insulation: Review of Effective Thermal Resistivity Values Used in ASCE Standard 32-01—Design and Construction of Frost-Protected Shallow Foundations

Abstract

Effective (design) thermal resistivity values for use of rigid, cellular polystyrene foam insulation in below-ground frost-protection applications play an important role in the success of the ASCE 32-01 standard. The ASCE 32-01 standard is currently recognized in U.S. model building codes as a cost-effective means of protecting building foundations against frost heave in regions with seasonal ground freezing and no permafrost. The long-term thermal performance of foundation insulation used for this purpose is, therefore, a critical building performance concern. This same concern also has relevance to sustained performance of below-ground insulation used for energy conservation purposes. This paper provides a critical review and analysis of data reported in the literature on below-ground thermal performance of rigid, cellular polystyrene foam insulations. These products can be molded expanded polystyrene or extruded polystyrene as defined by ASTM C578 in ASTM 2008 Standard. The findings serve to document and confirm effective thermal resistivity values originally incorporated into the ASCE 32-01 standard for frost protection of building foundations.