Summer overheating in Mediterranean cities: cooling strategies at the building and urban scale

Densely urbanized areas of our cities are even more affected by urban overheating risk, which determines an increase in ambient temperatures. This phenomenon is responsible for high cooling energy demands, local and global pollution, heat-related mortality, pedestrian discomfort, and peaks in electricity demands. Coastal cities are no exception, indeed, although these benefit of the thermoregulatory function of the sea and by the cool sea breeze, suffer from the effects of urban heat islands (UHI) in densely inhabited areas. This study concerns a historic neighborhood in Naples (Italy), the Chiaia district, which runs along part of the Neapolitan waterfront. The quarter is largely involved by an intense overheating phenomenon during the summer, registering air temperatures higher than 35 degrees C. To reduce this phenomenon, urban cooling strategies are evaluated, through a numerical model, to predict a reduction in temperature peaks without compromising the historical identity of the district. Spot-check temperature values, from the numerical model of "Chiaia district" were compared to spot-measured ones, just for an initial evaluation of model reliability, during a typical warm day of the summer. Then, urban cooling strategies involving outdoor building envelopes, namely high solar reflectance materials for roofs, green roofs and green walls, and urban vegetation at ground level are evaluated. Particular attention is paid to a green lung skirting the Neapolitan seafront and to its impact on the reduction of urban temperatures. The study shows the efficacy of the evaluated strategies for urban cooling in reducing the peaks of air temperatures and improving air quality.