Thermal investigation of thin precast concrete sandwich panels

Abstract

Thin, lightweight alternatives to standard precast concrete sandwich panels have received much research and design focus in recent years. Some designs have been structurally tested and validated. Much less focus has, however, been given to their thermal performance. This study thermally investigates thin, lightweight precast concrete sandwich cladding panels that embed high performance insulation between two thin concrete wythes. A sample thin design is experimentally tested using a hot plate apparatus to evaluate its thermal performance. Finite element modelling is then used to further investigate the common features of thin panel designs and potential areas of heat loss. The analysed representative thin sample sandwich panel (150 mm thick) achieves an average U-value of 0.324 W m−2 K−1; this is 16% lower than that of a typical 315 mm thick sandwich panel with 100 mm of polystyrene foam insulation. Thermal bridging is identified as a major source of heat loss in the thin wall design, accounting for up to 71% of the total thermal transmittance of the tested thin sandwich panel. In standard walls this is usually less than 20%. Some of the features of the tested design can be improved to significantly reduce the effect of the thermal bridging and reduce the U-value by 59% to 0.13 W m−2 K−1 in an optimised panel design.