Enhancing building wall thermal performance with phase change material and insulation: A comparative and synergistic assessment

The energy-saving effect of phase change materials (PCMs) and conventional thermal insulations has traditionally been considered separately, although a purposeful combination of the two could increase energy-savings. Therefore, this study investigated the energy benefits of PCM and conventional thermal insulation applied separately or in combination in a building external wall. A numerical model was developed and validated with analytical solution and experimental data. In the comparative analysis, PCM located on the interior side of the wall outperformed insulation for layer thicknesses ≤ LPCM= 16 mm. In the best case, PCM saved 38.2% more energy than insulation at a layer thickness of LINS= 6 mm. A parameter (ψ) defining the ratio of LPCM to LPCM + LINS was introduced. The synergistic effect evaluation revealed that using a composite of PCM and insulation (C5 configuration, ψ = 0.05) conserved up to 7.3% of energy compared to only insulation application (ψ = 0). Besides, configuration C6 with ψ = 0.15 provided 6.4% more energy saving than ψ = 0. Furthermore, the combined designs with 0 < ψ ≤ 0.6 outperformed ψ = 0 for C5, C6, and C10 configurations. Overall, a marginal positive effect on the energy saving was observed for the combined design compared to insulation only. Latent heat activation was critical for obtaining improved thermal performance.