Evaluating the cooling effect of urban street shading on ambient air temperatures in the built environment

Abstract

In recent times, Malta has seen rapid urban development relying on unsustainable grey infrastructure, prioritizing private car use over pedestrian experience. This car-centric approach, coupled with the harsh summer climate, makes walking through urban areas inconvenient and unpleasant. Consequently, people stay indoors in air-conditioned homes, venturing out only when temperatures drop. This increases building heat gains and cooling energy needs, discourages walking and cycling, and detracts from the enjoyment of outdoor spaces, negatively impacting human wellbeing. This study investigates the effects of urban shading on thermal comfort in public spaces through on-site measurements of ambient temperature and relative humidity in shaded and unshaded conditions. Furthermore, numerical modelling was also utilised to determine the effects of outdoor shading on conditions in indoor spaces, using the initially recorded outdoor thermal conditions. Results show that during the summer, unshaded areas reached ambient temperatures of up to 44°C, with shaded areas significantly cooler by 11°C. Despite this reduction, however, analysis of conditions in shaded areas still exceeded the thermal comfort zone, indicating the need for additional cooling strategies. In autumn, the comfort range was 25.7°C to 31.5°C, with indoor conditions remaining too cold in both shaded and unshaded scenarios, necessitating heating or additional clothing. Spring showed similar comfort ranges but with more variation in indoor temperatures, which were within the comfort zone with outdoor shading. During summer, shaded conditions brought excessively hot indoor temperatures down to within the comfort zone, reducing the need for additional cooling. Winter’s comfort zone ranged from 23.4°C to 29.9°C, with shaded conditions requiring heating until mid-afternoon but generally maintaining comfort later in the day. Survey data revealed that thermal comfort significantly impacts residents' transportation choices and willingness to engage with outdoor amenities. The findings suggest that integrating urban shading with other cooling methods can enhance thermal comfort, promote alternative transportation modes, and improve the overall quality of urban life. These insights contribute to global research on urban heat mitigation and inform policy recommendations for sustainable urban planning and infrastructure development.