Optimization of PCM-enhanced residential building envelopes in cold climates: Energy performance and cost-effectiveness analysis

• Developed efficient simulation-based optimization framework with convergence analysis. • PCM optimization balanced source energy use and cost in Canadian cold climates. • HVAC energy use, sizing, load profile, and efficiency analyzed under PCM use. • Economic analysis identified PCM investment priorities and viable future conditions. This study presents a techno-economic optimization of phase change material (PCM)-enhanced residential building envelopes in Canadian cold climates, aiming to minimize both annual source energy use and life-cycle cost. A multi-objective optimization framework was developed by coupling EnergyPlus simulations with the non-dominated sorting genetic algorithm (NSGA-II) and a custom data-logging mechanism. Thirteen PCM-related design variables were considered across four envelope types and four representative cities. The analysis also evaluated the potential downsizing of heating and cooling system capacities in a reference multi-family prototype building. Two objectives, annual source energy intensity and total cost, were optimized to explore trade-offs between energy performance and total cost. Results revealed a clear Pareto front, demonstrating the inherent compromise between energy savings and cost. Optimal configurations favored interior PCM placement, midpoint melting temperatures of 21∼24°C, and narrow melting ranges of 1∼3°C. PCM integration reduced both heating and cooling energy use and modestly decreased HVAC capacity requirements by flattening the cooling load profile, while exhibiting only limited peak-time shifting effects. Economic analysis showed that most current PCM products remain cost-ineffective, with simple payback periods typically exceeding 150 years. The break-even price analyses identified target PCM costs of approximately 1.3, 1.0, 0.85, and 0.65 $/kg for Edmonton, Vancouver, Toronto, and Montreal, respectively, to achieve practical feasibility. The proposed framework provided a robust approach for evaluating PCM investment strategies and offered broader insights into optimizing thermal storage-based envelope designs for peak-load management and energy efficiency in cold-climate buildings.