On the effect of summer heatwaves and urban overheating on building thermal-energy performance in central Italy

Local climate phenomena impose a serious threat to the built environment. In particular, urban heat island and heatwaves can significantly affect buildings’ thermal-energy performance. The purpose of this study is to investigate summer hot periods and their impact on building thermal-energy behavior in an urban area in Italy. To this aim, the statistical analysis of the microclimate variation during monitored hot periods is performed by the analysis of local weather parameters collected from a dedicated meteorological station. Moreover, the numerical analysis of representative Italian residential buildings is carried out to determine the role of such phenomena on indoor thermal comfort and cooling energy requirements, by considering the consequences arising from heatwaves due to the indoor overheating stress. The analysis showed a strong negative correlation between temperature and relative humidity during extreme hot periods (∼−0.92). Positive correlation was noted between temperature and solar irradiance (∼0.62) and temperature and wind velocity (∼0.33). The southern winds registered in normal hot periods reduced the heat stress by cooling-down the south-facing urban surfaces. The numerical analysis demonstrated higher indoor temperature for insulated buildings, requiring more than three times the cooling requirement of traditional non-insulated buildings in extreme hot periods and exacerbating the occupants’ vulnerability.