Integration of thermal-daylighting climate subzones and energy efficiency design optimization for office buildings

Existing building optimization designs mainly focus on balancing thermal comfort and energy efficiency, while few explore the coupled effect of daylighting, thermal and energy performance for synergistic optimization. This study was to propose a multi-objective framework for optimal designs for office buildings, achieving the trade-off between thermal, daylighting and energy performance. Given the varying thermal and daylighting conditions in the Hot Summer and Cold Winter (HSCW) zone of China, and the lack of refined subzones during building optimization designs, the meteorological data from 107 cities throughout this region was first collected; using heating degree day (HDD18), cooling degree day (CDD20) and annual global horizontal illuminance (GHI), four subzones were obtained based on cluster analysis. Nine building design variables were identified as key inputs through the global sensitivity analysis. Energy usage intensity (EUI), thermal discomfort percentage (TDP) and useful daylighting illuminance (UDI100-2000) were adopted as optimization objectives. The multi-criteria decision-making process was conducted to explore the recommended range and trade-off solutions for optimal variables for different climate subzones. The optimization solutions of high building airtightness (0.5 h−1) and thermal insulation of the exterior wall (0.22–0.27 W/m2 K) had positive effects on energy efficiency and thermal comfort, while WWR of the south/north facades and exterior shading enhance natural ventilation and daylighting uniformity. This work innovatively integrated climate subzones of thermal and daylighting into optimization process, and quantified their regional differences during passive designs, which benefit to the design, refurbishment and renovation of office buildings in the HSCW zone in China.