Mapping Vertical Greenery on Historic Buildings in Neighbourhoods with High Environmental Risks: A Case Study in Antwerp, Belgium

Ongoing urbanization has increased the impact of the urban heat island effect, air pollution, and noise pollution while limiting the space for green areas. Therefore an urgent action is required to mitigate these environmental risks. Vertical Greenery (VG) has emerged as a sustainable and viable solution across diverse contexts, but it is generally not always accepted for historic buildings by experts. The scepticism is rooted in concerns about the potential adverse effects on conservation practices and heritage values. Contrary to expert concerns, VG on historic buildings is seen as a response to reducing the urban heat island effect in high environmental risk areas by the users. We conducted a comprehensive study in Antwerp (Belgium), a city actively advocating for VG solutions. We selected three neighbourhoods, namely Historical Centre, Oud Berchem, and Borgerhout Intra Muros Zuid, where air pollution, noise, and heat stress are above the risk level. We documented the VG implementations in these three neighbourhoods through the use of GIS and field survey methods. The prevalence of VG in case sites was analysed based on factors such as the heritage status of buildings and the morphology of streets, which could pose challenges to the implementation of VG. The results suggest that VG is present in up to 14% of all buildings in the selected neighbourhoods. While in the Historical Centre, 59% of the buildings with VG have a heritage designation. As such, narrow streets and heritage designation do not prevent VG implementation in densely built neighbourhoods with green space deficits. While this study provides site-specific results, the analysis methods we used can guide policymakers and urban planners to explore VG's adaptability to historic buildings in the development of effective integration strategies.