Green Roof Systems: Characterization of a Laboratory Testing Method for Assessing Growing Media Thermal Conductivity

Green roofs performance have been widely investigated over the past few years, since they offer a series of benefits under different aspects: not only do they contribute to increase green areas inside the urban center from an environmental point of view, but also they meet several energy performance requirements, when they are well designed. In fact, these systems alter the heat flow through the roof covering, therefore affecting the energy balance inside the building. The majority of the studies present in literature have focused on characterizing extensive and intensive green roofs and their layer composition, on the other hand there is a lack of studies that pursue the assessment of these systems thermal performance from a more engineering point of view, with the target to set thermal conductivity and thermal resistance standards in order to use them as insulation components. The aim of the study presented in this paper is to propose a laboratory testing method that can be used to assess substrates thermal characteristics in order to find reference values for common growing media and also for testing the performance of new ones. This would provide more options to select from, also based on the availability of a specific material in different areas, increasing the environmental benefits that these systems already offer. A viable option is perhaps testing recycled and waste materials to assess how they would perform as green roof substrate layer. Further tests on green roof layers energy performance meant to define reference values would fill the gap between theoretical studies on their benefits and actual day to day use.