The impact of urban dry island on building energy consumption is overlooked compared to urban heat island in cold climate

A large number of literature reveals the impact of urban heat island on building energy consumption, however, the urban dry island impact on the energy demand is very limited. This study aimed to determine the urban-rural disparities in temperature (zT) and relative humidity (zRH) on sensible and latent heat loads (SHL, LHL) in a large city belonging to the cold climate zone of China. The results showed that apparent zT and zRH existed between the urban and rural areas, with higher T and lower RH in the urban area compared with those in the rural counterpart. The zT of the heating period (1.37 degrees C) is far higher than that of the cooling period (0.45 degrees C), whereas the zRH is almost same in the heating and cooling periods (-9 % vs -8 %). Due to the effect of zT, the urban SHL of office building was averagely lower 15.1 % than that in the rural area during the heating period, but only higher 4.6 % in the urban area compared with the rural area in the cooling period. By contrast, the decrease extent of LHL of office building between urban and rural areas in the cooling period (58.7 %) extremely exceeds the increase of LHL in the heating period (6.7 %) due to the zRH impact. Negative significant relationships between zT and the change of SHL from urban to rural areas, as well as between zRH and the change of LHL were found during the heating period, but being positive significant relationships during the cooling period. This study reveals that, in the cold climate zone, the LHL has large contribution to the total energy consumption of buildings, especially the LHL during the cooling period in urban area is much lower than that of the surrounding rural area, highlighting the need to fully consider the LHL in the design and operation of airconditioning system. In addition, this study shows the potential for improving energy efficiency of other building types or other cities in the cold climate zone by considering the UDI effect.