Enhancing building energy efficiency with thermal mass optimization

High-density urban buildings contain substantial thermal mass, storing significant energy and offering notable potential for heating energy savings. However, effectively harnessing this energy remains challenging due to the spatiotemporal variability of heat storage–release behavior in building components, which often misaligns with building operational demands. This study reveals that thermal mass tends to store heat when it is not needed and release it when buildings do not require it, especially in cities where some buildings are only occupied during the day and others at night. To address these challenges, this study proposes a novel thermal mass arrangement strategy, derived from extensive real-world data analysis. Significant variations in component thermal behavior across different operational schedules were first identified from data collected in 76 rooms. Subsequently, key factors influencing these variations were pinpointed using stepwise linear regression, informing optimization strategies developed through simulations. These strategies were then validated in cold regions using conduction transfer function models (error margin of 3.6 %), which confirmed their year-round effectiveness for both individual buildings with distinct occupancy patterns and groups of buildings. The results demonstrate that optimizing thermal mass arrangements tailored to specific building schedules can significantly enhance energy efficiency. Contrary to prior research advocating for the sole increase in thermal mass, this study indicates that without strategic guidelines, such measures may exacerbate thermal utilization inefficiencies, complementing existing research on thermal storage materials in buildings. Reducing excess heat storage is shown to be beneficial for daytime-use buildings, while nighttime-use buildings benefit from storing heat for evening use. Adjusting the quantity and orientation of thermal mass, alongside optimizing operational schedules, achieves 4–12 % energy savings, with greater benefits in high-solar-radiation areas.