The work investigates the Urban Heat Island (UHI) phenomenon and its effects on building energy performance using data from 23 weather stations in Rome (Italy). The processes are facilitated by an analysis of the urban fabric using a Geographic Information System (GIS) to provide correlations between urban features and UHI. The different weather-data were also used as input to perform dynamic simulations for estimating the heating and cooling energy needs of two typical residential buildings, characterized by different construction. The results reveal considerable differences regarding temperature, wind velocity and relative humidity, as a result of a prevailing UHI phenomenon during the whole year.
The temperature differences as a result of the UHI reach about 5.4 °C during the day and exceed 4.5 °C at night. The impacts on the buildings’ energy demand for heating and cooling are significant. For an old building, the heating energy demands showed percentage differences ranging from −33.28% to −4.51%, and the cooling energy needs showed variations from −5.33% to 93.25%. On the other hand, considering a more recent structure, variations from −37.73% to 0.22% were obtained for the heating energy needs, and differences from −2.72% to 63.31% were identified for the cooling energy demands.