Impact of building envelope design parameters on diurnal building anthropogenic heat emission

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 design. Based on a new method to determine QF,B [1], 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 8–15 h 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.