Investigating urban canyons, façade albedo, and pedestrian thermal comfort using microclimate model calculations

Abstract

Previous studies have shown a strong relationship between heat-related fatalities and ambient air temperature. This problem is expected to increase due to constant urbanization and the threat of global warming. Therefore, designing urban street canyons (USC) to be thermally comfortable is essential for a healthy urban life. This paper investigates the correlation between an urban street canyon’s aspect ratio and the albedo material of its surrounding buildings. The aim is to study which combination can successfully mitigate urban heat stress and create a thermally comfortable pedestrian microclimate. This research uses a comparative analysis that suggests the optimum albedo for different USC geometries. An ENVI-met model was used to simulate 9 scenarios for an idealized 2D USC with varying aspect ratios and albedo values. Air temperature, mean radiant temperature and Universal Thermal Climate Index (UTCI) were analyzed. Results show that a medium albedo value performs best thermally in all USCs. High albedo had 13.2% more combined thermal stress compared to medium albedo. However, high albedo performed much better in deep canyons than wider ones, with the average UTCI decreasing by about 4.8%-5.7% when used in deep canyons. Medium albedo should be exclusively used in wide canyons for minimal thermal stress. Practical application: This study provides a reference to the use of materials in urban street canyons of different aspect ratios to achieve good outdoor thermal comfort for pedestrians.