The Effectiveness of Cool and Green Roofs as Urban Heat Island Mitigation Strategies: A Case Study

To mitigate the impact of climate change, building designers have to mature novel strategies to mitigate the well-known urban heat island (UHI) effect. Built surfaces, often characterized by low albedo coefficients, absorb and store solar energy during the daytime, then they discharge such stored thermal energy to the surrounding during both day and night. Cooling the urbanized areas and so protecting them from the more and more frequent heat waves is one of the challenges that policy and governments have to tackle. This paper aims to identify the effectiveness of cool and green surfaces as strategies for diminishing the outdoor air temperature and enhancing the urban well-being conditions. To this purpose, a micro-scale analysis, based on a simulation study, was carried out in a neighborhood of Catania city. Several mitigation solutions were modeled and simulated though a holistic three- dimensional non hydrostatic model with the aim of assessing their effectiveness. Moreover, surveys and measurements in situ are used to calibrate and validate the model results. The outcomes display that the cool materials (roofs and pavements) allow to reduce by about 1.0°C the environmental temperatures during a reference hot summer’s day