Influence of urban morphology on potential of green roofs in regulating local microclimate: A case study of Liège, Belgium

Abstract

Urban microclimate varies for different urban morphologies in a city necessitating the assessment of impact of green roofs on the local microclimate in such typical morphologies. This paper explores the role of roof greening in regulating the local microclimate in Liège, Belgium, for nine realistic and unique urban morphological archetypes during a heatwave. The urban morphological archetypes are obtained based on a systematic data-driven approach using an extensive list of morphological parameters. Nine scenarios without green roofs and nine scenarios with green roofs are simulated using Solene-microclimat model. Green roofs are introduced only on the existing flat roofs identified using remote-sensing to analyse the realistic impact of roof greening. Our findings suggest that distinct morphologies in the archetypes result in distinctive impact of roof greening on these archetypes. For instance, green roofs can reduce surface temperature effectively in compact high-rise archetypes, whereas green roofs' potential to reduce air temperature is limited. While green roofs can effectively reduce surface and air temperature in compact low-rise archetypes, most compact low-rise archetypes are residential and have fewer flat roofs to green. However, large low-rise archetypes, which are predominantly industrial/commercial, can be retrofitted with green roofs, considering large potential of roof greening. This study provides insight into the interplay between urban morphology, realistic roof greening potential, and the UHI effect on local microclimate, improving our understanding of microclimate regulation with green roofs.