Drainage layer in green roofs: Proposal for the use of agricultural plastic waste

Green roof promises to become an increasingly important option for building owners and community planners because it can address many of the challenges facing urban residents. The success of the roof depends on the specific build-up of the green roof, therefore, special attention was focused on the identification and application of more environmentally friendly materials in green roofs. However, except the substrate, very few studies have denoted the potential to use reused materials for drainage layers, despite its important role in determining thermal and hydraulic performance of green roofs. This study analyzes the scientific literature on the use of innovative materials from the recovery/recycling of products for the drainage layer and propose the use of low-density polyethylene (LDPE) granules coming from the recycling of waste films used in agriculture for greenhouse roofing and mulching as innovative and sustainable drainage material in green roofs. In addition, the proposal concerns the possibility to enclose the plastic granular material into micro-perforated bags made of recycled polyethylene and to use the soil coming from washing of agricultural films as substrate in green roofs. This proposal will be further investigated by laboratory assessment on the thermo-physical properties of several polyethylene granules and by experimental set-up having the goal of assessing the thermal performance of different green roof technologies, in order to represent a suitable alternative to materials commercially used from an environmental, economic, and social point of view.