Optimizing Energy Performance of Phase-Change Material-Enhanced Building Envelopes Through Novel Performance Indicators
Ahmad A. Memon S.A.
August 2025Multidisciplinary Digital Publishing Institute (MDPI)
Buildings
2025#15Issue 15
Over recent decades, phase-change materials (PCMs) have gained prominence as latent-heat thermal energy storage systems in building envelopes because of their high energy density. However, only PCMs that complete a full daily charge–discharge cycle can deliver meaningful energy and carbon-emission savings. This simulation study introduces a methodology that simultaneously optimizes PCM integration for storage efficiency, indoor thermal comfort, and energy savings. Two new indicators are proposed: overall storage efficiency (ECn), which consolidates heating and cooling-efficiency ratios into a single value, and the performance factor (PF), which quantifies the PCM’s effectiveness in maintaining thermal comfort. Using EnergyPlus v8.9 coupled with DesignBuilder, a residential ASHRAE 90.1 mid-rise apartment was modeled in six warm-temperate (Cfb) European cities for the summer period from June 1 to August 31. Four paraffin PCMs (RT-22/25/28/31 HC, 20 mm thickness) were tested under natural and controlled ventilation strategies, with windows opening 50% when outdoor air was at least 2 °C cooler than indoors. Simulation outputs were validated against experimental cubicle data, yielding a mean absolute indoor temperature error ≤ 4.5%, well within the ±5% tolerance commonly accepted for building thermal simulations. The optimum configuration—RT-25 HC with temperature-controlled ventilation—achieved PF = 1.0 (100% comfort compliance) in all six cities and delivered summer cooling-energy savings of up to 3376 kWh in Paris, the highest among the locations studied. Carbon-emission reductions reached 2254 kg CO2-e year−1, and static payback periods remained below the assumed 50-year building life at a per kg PCM cost of USD 1. The ECn–PF framework, therefore, provides a transparent basis for selecting cost-effective, energy-efficient, and low-carbon PCM solutions in warm-temperate buildings.
controlled natural ventilation , economic evaluation , energy savings , environmental sustainability , night ventilation , novel indicators , phase-change materials (PCMs) , storage efficiency , thermal comfort
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Department of Civil and Environmental Engineering, Voiland College of Engineering and Architecture, Washington State University, Pullman, 99164, WA, United States
Department of Civil and Environmental Engineering, School of Engineering and Digital Sciences, Nazarbayev University, Astana, 010000, Kazakhstan
Department of Civil and Environmental Engineering
Department of Civil and Environmental Engineering
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