Impact of urban heat island on energy demand in buildings: Local climate zones in Nanjing

This study aims to assess the impact of neighborhood-scale urban heat island (UHI) on the energy performance of buildings. Hourly air temperature and relative humidity were continuously measured for three years in 10 neighborhoods of Nanjing, China, which were selected based on the Local Climate Zone (LCZ) scheme. Data collected from the LCZ sites and suburban meteorological stations were analyzed and used as inputs for building energy simulations. Two types of building use (residential and office) were investigated. For the 10 LCZ sites, the annual mean UHI intensity ranged from 0.4 degrees C to 2.2 degrees C in the nighttime (19:00-06:00), and from 0.3 degrees C to 0.9 degrees C in the daytime (07:00-18:00). The heat islands presented in the LCZ sites could increase the cooling demand of residential (office) buildings by 12-24% (9-14%) and reduce heating demand by 3-20% (5-20%), leading to an increase of 2-5% (2-6%) in annual total demand. Compared with residential buildings, office buildings were less sensitive to UHI with respect to cooling and heating demand. Analysis of the hottest and coldest days shows that the average daily peak cooling load of residential (office) buildings was increased by 6-14% (5-9%), and the average daily peak heating load was decreased by 4-15% (3-14%). The study indicates that the spatiotemporal variability of UHI at the local scale can exert different effects on the energy performance of buildings. In addition, this study emphasizes the importance of developing site-specific climatic data to reliably assess the energy performance of buildings in urban contexts.