Urban metabolism in transition: a dynamic modeling of stock-flow-service nexus in the built environment

Abstract Rapid urbanization has intensified construction activity, driving higher resource consumption and environmental pressures in cities. Understanding the urban metabolism of the building sector, specifically the stock-flow-service nexus, is essential for developing effective sustainability strategies. This study applies an integrated modeling framework, combining dynamic material flow analysis, and prospective life cycle assessment, to assess the long-term transitions of material stock, energy demand, and greenhouse gas (GHG) emissions in Hong Kong’s public rental housing (PRH) sector from 1950 to 2100. Results show that the PRH building stock expanded rapidly from the late 1970s and is anticipated to stabilize at around 49 million m 2 by 2050, marking a transition from a flow-intensive construction phase to a stock-maintenance phase focused on renewal. While the provision of housing services drives energy demand upward until mid-century, associated GHG emissions are expected to decouple and decline substantially, driven largely by grid decarbonization. These findings validate the importance of integrated modeling in understanding the stock-flow-service dynamic, providing a foundation for region-specific policy interventions aimed at sustainable urban development.