Green roofs in European climates. Are effective solutions for the energy savings in air-conditioning?

► Scarce literature investigates the technical-economical feasibility of green roofs. ► This paper provides a wide analysis of their energy/economical performances. ► The amount of required irrigation is a key node in order to achieve benefits. ► In cold climates, green-roofs allow good performances, both in summer and winter. ► In warm climates, green roofs are not advantageous for well-insulated buildings.