Impact of urban heat island mitigation measures on microclimate and pedestrian comfort in a dense urban district of Lebanon

Abstract

The interaction between microclimate and buildings is predominant in urban areas. Thus, the urbanization constitutes the main cause of UHI formation. During the last years, several studies exposed the critical effects of UHI in the Mediterranean climate. As a result, there is a need for sustainable systems and urban policies to reduce heat islands in urban areas. This paper aims to present the impact of some UHI mitigation strategies in a Mediterranean city, Beirut Lebanon. Numerical microclimate simulations of an existing Lebanese district of Dora in Beirut, are performed using ENVI-met software. The study focuses on the potential of UHI mitigation scenarios to create freshness in summer conditions. The strategies are based on the increase of green surfaces, on the installation of water spray and fountains, and on the increase of the albedo of the facades and roofs of the buildings. A focus is carried out on white models, dealing with the albedo modification of roads and buildings. The effect of the proposed strategies on the pedestrian comfort is also evaluated by using the physiologically equivalent temperature PET. Results pointed out that implementation of water features contributes to a significant reduction of ambient temperature reaching a maximum of 5 °C. In term of outdoor thermal comfort, the results showed the important role of green areas on the improvement of pedestrian comfort during daytime. Finally, this research supports a set of actions that could be helpful for urban designer to create cool islands in the Lebanese neighborhoods.