Lightweight extensive green roof for building renovation: Summer performance analysis and application in a living laboratory

•The green roof’s hygrothermal behaviour patterns are analysed through monitoring campaign.•Lightweight extensive sedum-covered green roof system shows a lower temperature profile respect to the traditional concrete tile widely used as a flat roof finishing.•The soil’s water content influences hygrothermal performance and increases the attenuation potential during summer.•The lightweight green roof is a valuable technical solution easily integrable in renovation project of existing buildings.•The renovation case study represents a practical example of green roof technology integration in a real environment.