Optimizing the spatial layout of phase change materials in porous bricks for superior thermal performance beyond dosage effects

The integration of phase change materials (PCMs) into porous bricks offers a promising avenue for enhancing building energy efficiency. However, prevailing design strategies frequently prioritize PCM dosage over spatial configuration, resulting in suboptimal performance. This study challenges that convention, demonstrating that spatial layout-rather than merely the amount of PCM-is the pivotal factor governing thermal regulation. Through systematic numerical simulations of ten distinct configurations, we reveal that strategically positioning a single PCM layer towards the interior reduces the inner surface temperature amplitude by 25.7% (from 12.69°C to 9.43°C). This is achieved by optimizing the temporal synergy between the PCM's phase change process and external thermal fluctuations. Furthermore, we quantitatively establish the law of diminishing marginal returns as PCM dosage increases. The optimal single inner-layer layout achieves a high latent heat utilization rate of 0.97, outperforming double- and triple-layer configurations (0.82 and 0.83, respectively) that suffer from ‘thermal shielding’ and incomplete phase activation. Crucially, a newly proposed Cost-Benefit Index (CBI) analysis reveals that this configuration maximizes economic efficiency, scoring 1.76 times higher than fully-filled models. These findings advocate a paradigm shift in energy-storage envelope design toward strategic spatiotemporal control.