The effect of balcony configurations on ACH and pollutant concentration in symmetrical and asymmetrical street canyons

Street canyons are critical spaces where air pollution from traffic accumulates, posing significant health risks to residents and pedestrians. The influence of building patterns on the ventilation and dispersion of pollutants in street canyons has been widely investigated. only a few studies have focused on the covering features of buildings, such as overhangs, wing walls, and balconies. Balconies, as integral architectural features, have a profound yet underexplored impact on airflow patterns and pollutant dispersion within these environments. Various studies have considered the effect of balconies on air quality within street canyons; however, little research has been conducted on the role of different balcony configurations in this context. Accordingly, this research investigates the impact of physical characteristics of balconies (depth, length, parapets, and wing walls) on ventilation and pollutant dispersion in symmetrical and asymmetrical street canyons. For this purpose, 15 balcony configurations will be selected as case studies, and their impact on pollutant concentration and air change per hour (ACH) will be examined within three types of canyons: symmetrical, step-up, and step-down. The results indicate that different balcony configurations in the step-down canyon led to a significant reduction in pollutant concentration. Increasing the balcony depth (depth 2.5 m) in all three canyon patterns increased ventilation and reduced pollutant emissions in the interior of the canyons. Removing the parapet around the balcony in all three canyon patterns reduced pollutants and increased the ACH within the canyon. In general, the effective use of various balcony configurations in symmetrical, step-up, and step-down canyons can improve ventilation capacity and pollutant removal, especially at the breathing level of pedestrians. These findings can assist urban designers in understanding the impact of balconies on enhancing ventilation capacity and pollutant removal in street canyons.