Optimizing Cross-Seasonal Microclimate for the Elderly: Synergistic Effects of Landscape Elements in China’s Hot-Summer and Cold-Winter Zone

This study addresses the critical challenge of optimizing outdoor thermal comfort for the aging population in old residential communities within China's hot-summer and cold-winter climate zones. Against the backdrop of urban regeneration and rapid demographic aging, it investigates how key landscape elements—ground reflectance, greening type, and pergola condition—influence the microclimate of community public spaces. The research employed an integrated methodology centered on numerical simulation. Using the ENVI-met software and an L₉(3⁴) orthogonal experimental design, it simulated the microclimatic effects of nine combined scenarios on typical summer and winter days for a case study in Nanjing. The comprehensive thermal comfort index, Physiological Equivalent Temperature (PET), was used as the primary evaluation indicator to assess the thermal comfort performance for elderly occupants, with the assistance of air temperature, wind speed, and relative humidity, and the results were analyzed via range analysis and ANOVA. The key findings indicate that: (1) Greening type and pergola condition are the dominant factors affecting microclimate and annual thermal comfort across seasons, while ground reflectance has a comparatively minor influence. (2) The combination of deciduous trees with lawn achieves the optimal cross-seasonal PET gain. It provides effective shading and cooling in summer while allowing beneficial solar penetration for warming in winter, substantially outperforming evergreen-dominated configurations. (3) The presence of a pergola consistently enhances comfort by providing essential shade in summer and acting as a windbreak in winter. The combination dominated by deciduous trees + lawn and pergola yield an overall PET gain 1.0967 ℃ higher than that of evergreen trees + shrub without pergola. This study provides evidence-based, elderly-specific landscape design strategies to inform the thermal environment optimization of public spaces in old residential areas undergoing renewal.