Mapping Vertical Greening on Urban Built Heritage Exposed to Environmental Stressors–A Case Study in Antwerp, Belgium

Urbanisation amplifies environmental stressors, including heat, air and noise pollution, while constraining horizontal space for green areas. Vertical greening (VG) offers a sustainable alternative to mitigate these environmental stressors and enhance the well-being of urban residents, particularly in densely built areas. However, heritage buildings are often excluded from VG initiatives due to concerns regarding potential damage caused by invasive plants. Nonetheless, these concerns mainly apply to abandoned structures lacking proper maintenance, overlooking the implementations of VG on urban built heritage. This study addresses this research gap through an evidence-based framework under three main research questions; first, by studying the presence of VG implementations in urban built heritage among neighbourhoods that lack green spaces and face high environmental stressors; second, by investigating the heritage designation status of buildings with VG; last, by analysing street morphologies where most VG implementations are observed. Antwerp, Belgium, a historical city actively promoting VG initiatives, is selected as the study area. Environmental risk index maps for historic urban areas are used for determining case studies among 63 neighbourhoods. VG implementations in three selected neighbourhoods are documented using GIS and field surveying methods. The results reveal that VG is implemented on up to 7–14% of buildings in these neighbourhoods. In the Historical Centre, 59% of these VG implementations are observed on heritage buildings. In densely built neighbourhoods with limited green space, neither narrow streets nor the heritage designation status of buildings hinders VG implementations. This illustrates the great potential for heritage buildings in adopting such types of nature-based solutions, nevertheless requiring proper guidance and integration strategies for implementing VG on heritage buildings. While these results are specific to the study locations, they provide valuable insights for policymakers and urban planners, supporting them to further explore the environmental contributions of VG on heritage buildings and create effective integration strategies.