Impact of urban albedo on microclimate and thermal comfort over a heat wave event in London

Abstract

This work investigates the potential of increasing the surface albedo of roads and buildings’ facades for mitigating thermal stress in London over heatwave events. The results are based on microclimate simulations with ENVImet (V4.4.3), validated using air temperature and radiation data (incoming and reflected) measured in a case study area of London. The comparison shows that ENVImet can accurately estimate the reflections within urban canyons in most cases and slightly overestimates the peak air temperature in urban canyons. The validated model is used to assess the impact of surface albedo on the Physiological Equivalent Temperature (PET) at the street level, considering the meteorological conditions of the heat wave on 29th June 2019. The results show that, at London’s latitude, increasing the albedo of facades has a negligible impact on the thermal environment at the street level. Conversely, reducing the reflectivity of facades and increasing the reflectivity of roads reduces the hours of extreme heat stress and lowers the PET values during the hottest hours of the day. This result can be explained by the impact of facades’ albedo on the multiple reflection of solar radiation within urban canyons.