Evaluating the role of the albedo of material and vegetation scenarios along the urban street canyon for improving pedestrian thermal comfort outdoors

Abstract

The undeniable role of urban valleys in improving pedestrian thermal comfort along the urban streets is crucial, especially in areas with hot summers. In this research, the parameters related to thermal comfort outdoors like air temperature (Ta), surface temperature (Ts), wind speed (Ws), sky view factor (SVF), mean radiant temperature (MRT), and physiological equivalent temperature (PET) in an urban street were analyzed using ENVI-met simulation. Besides, the effects of the albedo of pavement and the percent of Fraxinous Exceliour as the dominant tree in the study area were also examined to improve thermal comfort conditions. Simultaneously with the field measurements on the site, a questionnaire was used to determine the thermal comfort range of users in urban canyons. The study also integrates with ENVI-met microclimatic modeling to improve the thermal comfort in the urban street canyon, which was used to simulate the current situation and validated with field measurements, showing a good correlation. The result has revealed that SVF is not a precise indicator for crucial radiation exposure and thermal comfort conditions despite its wide application in previous studies. Further, a notable correlation between SVF and PET is observed solely throughout sunset. Additionally, the combination of the low-albedo pavements and covering half of the street with trees (Fraxinus excelsior) can produce the most effective conditions for thermal comfort. The simulation research reveals that albedo's effect on thermal comfort is less prominent than the tree cover. However, significant changes in albedo values and a decrease in urban heat have no significant impact on improving thermal comfort in urban canyons.