Exterior PCM performance response to multilevel thermal performance and climate change in office buildings

Integrating phase change materials (PCM) into building envelopes enhances their thermal inertia. With climate change intensifying and the need for high-performance buildings on the rise, it is crucial to understand PCM's effectiveness under these changing conditions. This study employs a multi-objective decision-making approach to optimize PCM parameters and conducts numerical simulations on office buildings to evaluate PCM's energy-saving across different climate zones and building levels. To assess PCM performance, the total energy savings of PCM (TES) and the latent heat energy savings based on phase-stabilized materials were analyzed. The impact of projected climate change on building loads under various Shared Socioeconomic Pathways was also modeled, revealing the responsiveness and performance of office buildings equipped with exterior PCM. Findings indicate that PCM's energy-saving potential varies across climate zones and building levels, with annual total load savings ranging from 0.45 to 4.33 kW.h/(m(2).a) and energy-saving rates between 0.38% and 8.19%. However, as building levels improve, PCM's energy-saving rates decline: for ultra-low energy buildings, savings range from 1.33% to 5.25%, while for nearly-zero energy buildings, they fall to 0.38%similar to 2.51%. Incorporating exterior PCM into an already high-performance building is less impactful unless combined with other designs factors, such as a large shape factor. Nonetheless, PCM's latent heat utilization rate remains above 30%, increasing with building performance. Under future climate projections, the PCM performance and latent heat utilization rate will deteriorate by over 10% in most areas by 2050, with the exception of Kunming. This research provides technical guidance for integrating PCM into future building designs to enhance energy efficiency and thermal resilience.