The energy retrofitting of heritage buildings is constrained by strict requirements on material compatibility, reversibility, and minimal intervention, limiting the use of conventional insulation systems. In this context, lime-based rendering mortars incorporating phase change materials (PCMs) offer a promising solution for enhancing thermal performance while respecting conservation principles. This study investigates the suitability of PCM-enhanced ternary lime-pozzolan-cement mortars through a combined laboratory and field-scale experimental approach, with particular emphasis on real-scale validation under outdoor conditions. Mortars incorporating microencapsulated PCMs were characterized in terms of microstructure, hygric and mechanical properties, thermal conductivity, and latent heat storage, alongside durability assessment under freeze-thaw and salt crystallization cycles. Thermal performance was evaluated using hot-box testing and monitored full-scale mock-ups exposed to real climatic conditions. The results show that PCM incorporation significantly reduces thermal conductivity (from ca. 0.63 to 0.30 W·m -1 ·K -1 ) while providing latent heat storage up to 2.7 J·g -1 . Durability performance was maintained or improved compared to reference mortars. Both laboratory and field-scale results demonstrate the ability of PCM-enhanced mortars to attenuate temperature fluctuations, leading to smoother internal temperature profiles and reduced thermal peaks under real environmental conditions. Overall, the findings confirm that PCM-enhanced ternary lime-based mortars can provide passive thermal buffering while maintaining compatibility with heritage substrates, supporting their application in conservation-oriented energy retrofitting strategies. • PCM-enhanced lime-cement mortars developed for heritage thermal retrofitting. • Thermal conductivity reduced by up to ca. 50% compared to reference mortar. • Up to 5.3% reduction in cyclic peak-to-peak temperature amplitude. • Field monitoring confirms a reduction of indoor temperature fluctuations of approximately 38% in the PCM-enhanced mock-up. • Multi-criteria ranking identifies optimal PCM formulations for façade use.
Kyriakou et al. (Wed,) studied this question.