How does building height optimize the summer thermal environment in shaded zones? A microscale simulation study in a hot-humid climate

Building shadows enhance summer outdoor thermal comfort, yet the precise microclimatic response threshold driven solely by building height remains unclear. To address this, this study constructed a quantitative analytical framework isolating building height as the primary variable, with orientation and surface material as moderating variables. Using ENVI-met simulations on a Guangzhou residential prototype across nine building heights (3–11 stories), five orientations, and three surface types (dry brick, concrete, grass), quadratic regression models were established to evaluate diurnal Physiological Equivalent Temperature (PET) variations under Typical Meteorological Year data. Key findings reveal that: (1) Increasing building height significantly reduces shaded daytime mean PET, with an 11-story south-facing building exhibiting a PET 3.01 °C lower than a 3-story counterpart; (2) orientation modulates PET magnitudes (south-facing yields the highest PET, whereas east/west deviations enhance cooling) without altering the declining height-PET trend; and (3) surface materials modify PET levels (dry brick > concrete > grass) while maintaining the overall height-based relationship. These results offer evidence-based guidance for microclimatic optimization in hot-humid climates.