Thermophysical characterization and life cycle assessment of two alternative green roof systems

Among the ever growing number of different strategies investigated and developed toward the environmental impacts mitigation, green roofs keep on being considered one of the most beneficial. Despite the continuous interest for these systems and the extensive research on the effects of their implementation, not so many recent studies have focused on improving the design of those that have now become traditional green roof systems, even though issues such as complex installation and high costs have not been overcome, at the expenses of average users. Also, if in depth assessments of green roofs environmental impacts have been conducted globally, there is still a lack of comprehensive studies that analyze green roofs from different aspects at same time. Many authors have in fact carried out detailed studies on either one of the benefits that they offer, such as increase of green spaces in urban areas, pollutants reduction in water and air, thermal damping at building and urban scale, etc. While some appraise the potential use of recycled material for green roofs construction, others focus on short-term benefits, such as the increase of green urban spaces, overlooking the environmental footprint determined by the materials and resources used in the construction of these systems. The study presented in this paper focuses on the thermophysical characterization and the LCA analysis of a proposed hydroponic green roof system (HGRS) design, in which the vegetation is grown through a soilless cultivation method, where only water is used as a substrate, built through software modelling. Then, a comparative analysis with a traditional extensive green roof model is carried out, with regards to both the energy and environmental aspects. Results from both the thermophysical characterization and the comparative LCA study on the two models show that the proposed hydroponic green roof system has the potential to reduce the impacts determined by traditional green roofs, linked to the complexity of their design, hence representing a feasible alternative to green coverage techniques.