A detailed and integrated presentation of the green roof systems is provided in the present paper. Aiming to analyse a specific urban case study, we describe the basic architectural and scientific principles that characterize its performance and efficiency. Furthermore, a state of the art presentation of the system is provided, including the presentation of several case studies as well as a selection and description of plants that usually are extensively used in the green roof system all over the world. Energy and environmental investigation. data of the green roof system performance in an office building located in the greater Athens area are provided. The energy efficiency was examined by calculating the energy savings through an accurate dynamic mathematical model. The thermal performance investigation showed a significant reduction of the building's cooling load during the summer period arriving at approximately 40%. Moreover, the influence of the green roof system in the building's heating load was fount insignificant, and this can be regarded as a great advantage of the system as any interference in the building shell for the reduction of cooling load leads usually to an increase of its heating load. (c) 2007 Elsevier Ltd. All rights reserved.