The Leeds urban heat island and its implications for energy use and thermal comfort

Urban heat islands are evident throughout the world and may become more problematic in temperate climates as global warming continues. This paper characterizes the urban heat island of Leeds, a city in the temperate maritime climate of the UK. Measured weather data from rural and urban sites have been used to quantify the heat island and to create building simulation weather files for the summer of 2013. These weather files have been used to model the impact on energy consumption and thermal comfort in notional non-domestic and domestic buildings, including a hotel, office, house and apartment. The heat island intensity is found to be greatest at night, with the peak in this data set reaching 5.9 °C at 20:00 on 2nd August 2013, with an average peak value of 2.3 °C occurring at the same hour for the case study period. Daytime temperatures were however similar at urban and rural sites. In the notional hotel building, air conditioning costs were increased by up to 40% due to night-time loads whereas consumption in the notional office was similar in all locations. Air temperature, and especially night-time temperature, increased in the domestic examples by an average of approximately 95 additional hours above 25 °C. This work expands knowledge by characterizing the Leeds urban heat island, demonstrating the importance of rural reference site selection for city regions that span a range of altitude, quantifying the gap in building performance when using regional or city centre weather files, and linking building occupancy patterns to the diurnal profile of the urban heat island.