Zoysia Soil-Less Green Roof’s Performance: A Life Cycle Assessment

The use of green roofs is demonstrated to improve the energy performance of buildings, increase biodiversity, reduce environmental impacts of urban areas, and mitigate climate change phenomena. Their use on a large scale is desirable in the coming years. Still, the choice of the most suitable green roof design solution should also consider the impacts of their production. Within this study, the Life Cycle Assessment methodology was used to evaluate the environmental impact of a particular typology of soil-less green roofs ideated by an Italian company. In this lightweight green roof, the growing medium is replaced by recycled felt layers, filtration is guaranteed by geotextile, and a closed-loop sub-irrigation system fertilises the pre-growth lawn placed on the top. The extremely low weight of this system suggests an optimal use in building retrofitting scenarios, but its environmental implication was not known. The environmental impact of this product has been assessed with an attributional cradle-to-gate approach through four different methodologies (ReCiPe midpoint and endpoint H V1.1, Ecological footprint V1.01, and IPCC 2013 GWP 100y V1.0) using the ecoinvent v3, Agri-footprint 1.0, and ELCD database on the SimaPro 8.4.4.0 software. The IPCC method has shown a Global Warming Potential of 7.66 kg of CO2 eq. for 1 m² of Pratotetto® green roof; however, the reuse of waste materials from the textile industry must be considered.