Thermo-economic assessment of a double-layer phase-change material in building roofs in a semi-arid climate

Thermal-performance assessment of a concrete roof with double macroencapsulated phase-change material (PCM) layers on the interior concrete surface in a semi-arid weather is herein reported. The roof was numerically analysed through computational fluid dynamics simulations using three models: a model with base concrete (RC), one with a concrete roof and one PCM layer (RC-PCMi) and one with a concrete roof and two PCM layers (RC-PCMi-PCMj). Numerical analysis was conducted for the warmest, coldest, and typical days of the year. Results indicated that double-layer configurations exhibit the best thermal performance with indoor heat flux reductions of 24.8 % (RC-PCM25-PCM29), 60.1 % (RC-PCM29-PCM25) and 57.9 % (RC-PCM29-PCM25) compared to those corresponding to the base case for the warmest, coldest and typical days, respectively. Furthermore, the configuration RC-PCM29-PCM25 delivered the best annual thermal performance, representing energy savings of 26.2 % compared to that for the case base. Moreover, considering a roof area of 36 m2 of a building located in Monterrey city, the payback period will be up to 3.45 years with an internal rate of return of 29.0 %. Based on the annual assessment, carbon emissions savings of the passive building roof system seem promising to steer the construction industry towards sustainability and net zero pathways.