Abstract/Summary

Anthropogenic heat fluxes from buildings (QF, B) are a major source of additional heating in cities, but vary both spatially and temporally. Knowledge of temporal variations of QF, B is critical to modulate urban climate through appropriate building designs. Based on a new method to determine QF, B (Liu et al., 2022), this study investigates the influences of building envelope design parameters on both magnitude and diurnal pattern of QF, B by season through parametric building energy modelling in Beijing. Using K-mean clustering, the distinctly representative diurnal patterns of QF, B in each season are identified. With classification-based analysis, we rank building parameters to understand their roles in causing these distinct QF, B patterns. We conclude that: (1) the most important building parameters influencing QF, B are U-value and thermal mass. (2) U-values effectively modulate both diurnal pattern and daily magnitude in all seasons. Buildings with small U-value (e.g., U-0.2) have lower daily energy consumption, resulting in an up to 73% reduction in QF, B daily mean in winter. (3) Thermal mass is more important in autumn/spring QF, B. It can both reduce the daily peak by up to 68% and shift the diurnal pattern dominated by mechanical cooling (peak during 15:00-17:00) into natural ventilation (peak during 01:00-06:00) with an 8-15h lag. (4) Combined with natural ventilation, appropriate building envelope designs (e.g., small U-value with lightweight fabric) should be considered to achieve both building energy-saving and improving outdoor thermal environment. Our results could help identify useful building design strategies to mitigate urban warming/cold in the periods that are hot or cold in cities.