Outdoor open spaces are essential for daily activities in ageing rural environments, yet the thermal effectiveness of vegetation under varying structural configurations remains unclear. Most existing Outdoor Thermal Comfort studies focus on dense urban canyons; the present study addresses this gap by examining a complexity threshold in vegetation cooling under high-SVF rural conditions and the radiation–ventilation trade-off that underlies it. An ENVI-met model was calibrated using field data from a typical village on the North China Plain and 17 vegetation scenarios were simulated. The findings reveal a non-linear relationship between vegetation complexity and cooling efficiency. A threshold of complexity was observed: the cooling performance declined with an increase in stratification from a double-layer (Scenario 12) to a triple-layer (Scenario 14) structure, with the change in mean radiant temperature (∆T_mrt) dropping from 23.16 °C to 21.10 °C. This is due to a radiation–ventilation trade-off, in which denser vegetation increases shading but reduces near-surface ventilation. Dense arrangements exhibit a heat trap effect, with the long-wave radiation flux changing from a cooling (−3.42 K/h) to a heating (+2.11 K/h) state. The results show a threshold effect in vegetation cooling and that thermal comfort is not necessarily enhanced by increased complexity. A shaded-canopy and permeable-understory structure is found to be optimal. The findings inform vegetation design in climate-adaptive rural settings.

Outdoor thermal comfort (OTC) influences how older adults use public spaces, yet evidence from rural settings remains limited. This study investigated OTC and adaptive behavior among rural older adults who actively used public spaces during the transitional season in Xixin Village, central China. Field measurements, 196 questionnaire responses, behavioral observations, and ENVI-met scenario simulations were combined. The neutral Physiological Equivalent Temperature was 27.4 \(^\circ\)C (95% CI 27.0–28.2 \(^\circ\)C), and the upper boundary of the 90% thermal acceptability range was 29.8 \(^\circ\)C. Because no PET values below 21.1 \(^\circ\)C were observed, the lower boundary and full width of this range could not be determined. Outdoor activity showed two daily peaks in the cooler morning and late afternoon, and respondents favored shaded, ventilated spaces. They also preferred medium-height, moderately dense, formally arranged evergreen trees. Under the tested clear-sky conditions, the combined S2 landscape scenario extended the simulated duration below the upper acceptability threshold at the frequently used EW street by approximately 2.7 h. The findings apply to active outdoor-space users in one village and identify design directions that require multi-site and multi-season validation.