Effects of street geometries on building cooling demand in Nanjing, China

Abstract

Urban heat island (UHI) effects are generally related to the urban morphology and urban design parameters such as street and building geometry. Especially in tropical and subtropical regions, the dense urban morphology usually results in not only an increase in temperature, but also the excessive building energy consumption. This paper presents a study on the influence of urban design parameters, such as street aspect ratios and orientations, on building cooling demands in the central area of cities. In this study, building energy simulations were conducted based on various urban scenarios characterized by different canyon geometries by using HTB2 and the Virvil plugin. The weather data needed in the energy simulation were obtained from the ENVI-met calculations. The energy results presented in this study suggest that the potential energy savings could be achieved through the optimization of urban design. Some basic principles are suggested for the street design in subtropical areas with similar climate conditions as Nanjing city. Furthermore, the cooling demands based on the localized and recorded weather data were both investigated and compared. An approximately 20% difference in cooling demand could be caused by the disparities between these two sets of weather data. The comparative analysis of two sets of energy results highlights the importance of implementing localized weather data in building energy simulations.