A decision support tool for calculating effective shading in urban streets

In times of climate change a strong effort should be made to enhance thermal conditions within cities to create livable environments. Shading in urban open spaces has been recognized as an important parameter in modifying microclimatic conditions and enhancing thermal comfort particularly in hot regions. When designed appropriately, shading can mitigate the Urban Heat Island (UHI), enhance pedestrian thermal comfort and affect outdoor activities. A decision support tool (DST) was developed for evaluating the minimum shading coverage required, by trees or other shading devices, to improve thermal comfort in streets during the most critical hours of the day. The presented DST accounts for the density of tree-canopies or the albedo of various materials used for shading devices. To develop the index, a set of climatic simulations was run using the Green CTTC model and thermal comfort was determined by the PET index. Based on the simulations Open-space Shading Coefficients (OSC) were computed and used to develop an Open-space Shading Index (OSI). The city of Tel-Aviv, characterized by a hot-humid climate, was selected as a case study. Results demonstrate the viability of the index as a DST for assessing the extent of shading required to achieve thermal comfort in urban streets.