Properties of PCM-based composites developed for the exterior finishes of building walls

Phase change materials (PCM) are widely known for their high thermal storage capabilities. They are generally utilized to increase the thermal mass of buildings’ lightweight materials, which improves their thermal performance and reduces the need for air-conditioning systems. PCM layers are commonly applied to the buildings’ interior parts, close to the indoor environment, which helps regulate the indoor temperature. However, few studies reported that PCM application on the exterior of the envelopes increases their thermal insulation, which can reduce the outdoor heat gain. Therefore, this study aims to develop PCM-based composites for the exterior finishes of building walls. To this end, microencapsulated PCM was integrated into the cement render and foamed concrete with different fractions. The developed composites were tested, evaluated, and compared to the composites without PCM integration. The results showed that PCM integration into foamed concrete reduced the density and thermal conductivity to 896 kg/m³ and 0.18 W/mK, respectively, i.e., lower by 50% and 86% compared to the conventional cement render. Besides, PCM integration added thermal energy storage of 38 J/g to the composite, which can improve its thermal mass. Although the compressive strength decreased by 53% with PCM integration into the cement render, it increased by 28–49.7% with PCM integration into foamed concrete due to PCM capsules substituting some of the air gaps. The findings of this study demonstrate a high potential of using PCM-based foamed concrete to produce lightweight cladding panels for building exteriors with improved thermal insulation and thermal mass to reduce external heat gain.