Highlights The maximum urban heat island intensity(UHI) reaches 4.3°C during summer  During daytime, air temperatures at the street level are higher than the roof level  The sea breeze has a positive effect on the roof level temperatures during summer  The UHI determines an average increase of the cooling load between 18% and 28%  The energy impact of the UHI is more relevant for higher solar gains Abstract: The Urban Heat Island (UHI) effect is particularly concerning in Mediterranean zone, as climate change and UHI scenarios foresee a fast growth of energy consumption for next years, due to the widespread of air conditioning systems and the increase of cooling demand. The UHI intensity is thus a key variable for the prediction of energy needs in urban areas.This study investigates the intensity of UHI in Barcelona (Spain), the densest Mediterranean coastal city, and its impact on cooling demand of residential buildings.The experimental analysis is based on temperature data from rural and urban Weather Stations and field measurements at street level. The maximum average UHI intensity is found to be 2.8 °C in winter and 1.7°C in summer, reaching 4.3°C at street level. Simulations performed with EnergyPlus indicate that the UHI intensity increases the sensible cooling load of residential buildings by around 18% to 28%, depending on UHI intensity, amount of solar gains and cooling set point.In the light of the results, the UHI intensity in Mediterranean context should be properly considered in performing energy evaluations for urban contexts, since standard meteorological data from airport weather stations are not found to be accurate enough.

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This work explores the double effect of urban compactness on buildings energy performance in Mediterranean climate, namely the increase of urban heat island (UHI) intensity and the decrease of solar radiation availability on the building façades. The energy demand of a test apartment has been calculated considering the variability of UHI intensity and solar radiation in different urban textures. Results show robust relationships between the energy demand and the texture’s site coverage ratio, which demonstrate that rather compact urban textures are more energy efficient than less dense urban patterns in Mediterranean climate.Peer ReviewedPostprint (published version