Urban Densification and Urban Climate Change – Assessing Interaction through DensificationScenarios and Climate Simulations

The paper discusses interrelations of urban densification and urban climate under global warming conditions by means of microclimate simulations as well as urban densification scenarios, referring to two research projects exploring test areas in Vienna and Linz, Austria. The impact of the extension of building heights on microclimate in densely urbanized areas is tested applying 3D city models describing building height distribution, surface properties and open space characteristics. In Vienna the densification impact on the local climate is explored for a larger study area by extruding the buildings’ footprints towards the maximum height as allowed by the current zoning regulations. In Linz the urban densification impact on the local climate is tested by adding high-rise buildings which are planned to be developed in a selected neighbourhood. Building height extension scenarios allow on the one side examining the densification potential to create new residential floorspace without requiring additional building land and on the other side to investigate the impact of densification on climate conditions by modelling the effects on heat storage during sunlight hours, nocturnal heat radiation from buildings and air flow. Microclimate simulations show significant differences in the diurnal variation pattern of the mean radiant temperature depending on increase or decrease of shading and heat storage effects due to densification.