Building integrated vegetation effect on micro-climate conditions for urban heat island adaptation. Lesson learned from Turin and Rome case studies

The proposed study investigates the effect of urban heat island mitigation scenarios by applying extensive green roofs, green façades, and living walls to two built areas within Turin and Rome, Italy. Three mitigation scenarios and a baseline one have been developed in ENVI-met software for each built area and run for a typical winter day, summer day, and summer day with a heat wave. The simulation results show that building integrated vegetation technology-application on a single building has an irrelevant effect on local temperatures; contrariwise, building integrated vegetation technology-wide application can effectively mitigate urban warming. Furthermore, the effect of green roofs and green walls on urban temperature is negligible in winter, likely because of the limited plant activity and the reduced amount of incoming solar radiation. Results also show that green façades are more effective than green roofs in mitigating pedestrian-level air temperature when installed on high-rise buildings, and green walls are more beneficial in mitigating summer urban heat island when installed in canyons parallel to wind direction than in perpendicular ones. Depending on the mitigation scenario, average decreases in urban temperatures up to 1 °C can be reached in the whole selected built area, alleviating urban warming.