Impact of vertical green façades on urban heat island mitigation and outdoor air quality

• Vertical green façade reduces the surface temperature of buildings. • Vertical green façade decreases the temperature fluctuations on the façade. • There is decrease in ambient PM2.5 and PM10 levels under dry conditions. • No significant ambient temperature difference was found between the green façade and reference wall, except when shading or other environmental factors were absent. This study investigates the effectiveness of vertical green façades (VGF) in mitigating the urban heat island (UHI) effect and enhancing air quality. It further examines the influence of structural, spatial, and environmental parameters on the performance of VGFs. Field measurements were conducted on four living walls and one green façade situated in diverse urban contexts across two climate zones: temperate oceanic (Cfb) and humid continental (Dfb). The results demonstrate that VGFs significantly reduce building surface temperatures during summer, with living walls achieving reductions of up to 13.7 °C and green façades up to 13.1 °C. Additionally, VGFs contributed to notable decreases in particulate matter concentrations, with average reductions of 1.04 µg/m 3 for PM2.5 and 2.05 µg/m 3 for PM10. The findings underscore the importance of understanding the interplay between design and environmental parameters to accurately predict VGF performance. Further empirical research is required to elucidate the mechanisms of particulate matter deposition and to refine assessments of environmental factors influencing VGF efficacy in outdoor urban environments.