Several façade types for mitigating urban heat island intensity

The phenomenon of elevated air temperatures in urban regions, known as urban heat islands (UHI), is closely linked to the thermal properties of building façades in those areas. Heavyweight materials, such as concrete and brick, absorb and release the heat escalating the intensity of UHI. We studied the thermal behaviour of façade types based on various concepts, namely, thermal absorption (brick wall), thermal utilisation (green wall and submerged aluminium composite panels [ACP]), reflection (reflective coating), insulation (expanded polystyrene), and shading or covering (ACP and cement board panel), on the east and west walls of a building. Direct field measurements included surface temperature, solar irradiation, cloud cover, globe temperature, air temperature, wind velocity, and relative humidity near the surface, were conducted in April and July 2021 (7 d monitoring period) on the walls of 90 × 90 cm specimens. The effectiveness of mitigating the urban heat island intensity (UHII) of the façade types in a residential area was simulated using ENVI-met 4.4.5 software. The results showed that heat utilisation (green walls) and reflection effectively reduced UHII. Green walls lowered temperatures by an average of 0.65 °C during the monitoring period (maximum 0.99 °C) through evapotranspiration, whereas the reflective coating reduced by 0.53 °C on average (maximum 1.89 °C) during low sun angles in the morning and afternoon. These findings will be helpful for architects, urban planners, and policymakers to contribute to UHI mitigation. •Mitigation technology to control the urban heat island intensity is urgently needed.•The concepts of absorber, reflector, insulation, heat utilisation, and covering were tested.•The facade concepts reduce the intensity of urban heat islands differently.•Green walls and reflective coating are the most effective mitigation technology.