Evaluating phase change materials for thermal load reduction in high occupancy public buildings: A comprehensive DesignBuilder based parametric analysis

This study evaluates the energy performance of Phase Change Materials (PCMs) in high-occupancy, windowless assembly buildings, which are uniquely characterized by intermittent internal heat gains and dominant mechanical ventilation loads. Using the Saei Hall in Tehran (an 884 m 2 modeled zone) as a real-world case study, dynamic whole-building energy simulations were conducted via EnergyPlus utilizing the Conduction Finite Difference (CondFD) algorithm. Three commercial PCM series (BioPCM, Infinite, and Winco) were parametrically assessed under uniform and novel hybrid (cascaded) configurations. The findings explicitly challenge the conventional "diminishing returns" hypothesis; multi-layer integrations, specifically the Infinite 21°C double-layer, demonstrated profound efficacy by reducing sensible cooling by 4.69% and sensible heating by 82.34%. A critical discovery of this research is the "Quenching Effect" a phenomenon where static mechanical ventilation schedules (ASHRAE 62.1) severely conflict with diurnal PCM phase cycles, causing premature depletion of latent heat and inducing massive energy penalties. Furthermore, the implementation of a cascaded hybrid configuration (21°C /27°C) successfully mitigated the "thermal entrapment" frequently observed in high-melting-point models (29°C), yielding an optimal 14.71% savings in heating demand. Cross-climatic evaluations confirmed the system's peak performance in Tehran's moderate semi-arid climate, while revealing complete functional failure in hot-humid regions. Ultimately, this research underscores the imperative paradigm shift from static passive envelope design to dynamic, phase-responsive Building Management Systems (BMS) to unlock the full latent thermal potential of PCMs in ventilation-dominated environments.