The effect of urban shading and canyon geometry on outdoor thermal comfort in hot climates: A case study of Ahvaz, Iran

Abstract

This study investigated the role of urban geometry and urban shading in improving the pedestrians’ thermal comfort in hot climate of Ahvaz, Iran. Six urban canyons are selected in Ahvaz. To determine the outdoor thermal comfort range, micrometeorological measurements and questionnaire survey were conducted in July 2018. ENVI-met is used to investigate the role of urban geometry and urban shadings. To evaluate the outdoor thermal comfort, physiologically equivalent temperature (PET) is calculated using RayMan. Using the results of the field studies, the outdoor thermal comfort range in Ahvaz is obtained within 19.6 °C to 30.9 °C PET. Simulation results show that the closer the canyon orientation is to the north-south direction, the lower the air temperature (Ta) and mean radiant temperature (MRT) are. Also, by reducing the canyon aspect ratio, PET increases as well. Urban shadings decreased MRT and PET up to 34 °C and 17.6 °C, respectively. In contrast, shadings did not affect the air temperature, significantly. PET reduction caused by shadings is more notable in east-west canyons, as well as in wider canyons. MRT and PET in all cases are highly correlated to SVF. The observations showed no strong correlation between Ta, relative humidity, and wind speed, with SVF in all canyons.