Hygrothermal Optimization of Bio‐Based Walls With Phase Change Materials

This study investigates the hydrothermal behavior of composite walls combining bio‐based materials (hemp concrete and date palm concrete) and Phase Change Materials (PCM). A numerical model based on a 2D planar domain was developed using ANSYS Fluent to simulate the one‐dimensional (1D) concurrent heat and moisture transfer in the multilayer wall structures. The analysis focused on temperature amplitude, time delay, relative humidity (RH) fluctuations, and energy storage efficiency. The results indicate that the PCM indirectly improves moisture regulation by dampening temperature fluctuations in adjacent bio‐based layers, which stabilizes indoor RH. Whereby the greatest performance is achieved if the PCM are located in the middle layer of the envelope. Time delay of the peak temperature was delayed was 6.5 h with hempcrete and 6.9 h with date palm concrete, reflecting that these values were higher by 62.5% and 53.3% compared to the reference, respectively. Besides, temperature amplitude was lessened by 18.9% with hempcrete and 64.6% with date palm concrete. Moreover, the attenuation of RH fluctuation was very significant. There, the maximum amplitude was 55% for date palm concrete. The research shows that using the PCM indirectly enhances moisture regulation by dampening temperature variations in adjacent bio‐based materials, thereby limiting indoor humidity fluctuations. The suggestions of the engineering branch to this design incorporate the best PCM placement and the anticipated comfort level, thus constituting valuable directives for the layout of energy‐saving building envelopes.