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 <= L-PCM = 16 mm. In the best case, PCM saved 38.2% more energy than insulation at a layer thickness of L-INS = 6 mm. A parameter (psi) defining the ratio of L-PCM to L-PCM + L-INS was introduced. The synergistic effect evaluation revealed that using a composite of PCM and insulation (C5 configuration, psi = 0.05) conserved up to 7.3% of energy compared to only insulation application (psi = 0). Besides, configuration C6 with psi = 0.15 provided 6.4% more energy saving than psi = 0. Furthermore, the combined designs with 0 < psi <= 0.6 outperformed psi = 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.