Evaluation of the thermal indices and thermal comfort improvement by different vegetation species and materials in a medium-sized urban park

Abstract

Regarding the significant impact of thermal comfort on users’ attendance in urban parks, there is an intense interest in studies on the outdoor thermal comfort in parks especially in regions with hot summers. This research examines the determinant factors of thermal environment and also strategies related to albedo and greenery in a medium-scale park using ENVI-met software. In this regard, the environmental situation is analyzed using air (Ta) and surface temperature (Ts), wind speed (WS), sky view factor (SVF), the mean radiant temperature (MRT), and physiological equivalent temperature (PET). Subsequently, low- and high-albedo pavements, plane and pine trees, and Buxus shrubs strategies are investigated that can significantly influence the parameters. According to the results, SVF is not a precise indicator for determining radiation exposure and thermal comfort conditions despite its wide application in previous studies. Further, there is a significant correlation between SVF and PET only during sunlight and sunset. In addition, the best thermal comfort condition can be reached by combining the low-albedo pavements, and trees with wide crowns and high trunks. The crown height from the ground is an important factor due to its effect on the airflow that can also counteract the impact of slightly increased radiation. Field investigation and simulation studies reveal that the effect of albedo on thermal comfort is lower than the vegetation coverage. Nevertheless, the significant changes in albedo values and urban heat island mitigation do not have any considerable effect on thermal comfort improvement in urban parks.