Green roofs as a nature-based solution for improving urban sustainability: Progress and perspectives

Green roofs are artificial ecosystems that provide a nature-based solution to environmental challenges such as climate change and the urban heat island. Green roofs aid in the conservation of both cooling and heating energy; deposition of particulates and mitigation of air pollution; control of runoff and water pollution; promotion of biodiversity; and provision of aesthetic and health benefits. This research is a holistic review of the green roof literature and provides a global perspective of the subject with a classification of modelling studies; and an extensive review of contributions to energy conservation, carbon sequestration, mitigation of air pollutants, runoff control; and urban noise reduction. The review covers the system's thermal performance modelling through several methodologies; experimental studies; parametric studies to assess the impact of various pa-rameters on the system's energy efficiency using several configuration parameters such as leaf area, foliage height and density, plant coverage, roof insulation, soil thickness, and irrigation; energy benefits; and envi-ronmental benefits including air pollutants mitigation, carbon sequestration, runoff control and urban noise reduction. Finally, review was complemented with a life cycle assessment study of green roofs, which examined the extraction of raw materials, manufacturing and construction, transportation, and disposal.Green roofs can reduce the cooling load by up to 70%, decrease the indoor temperature achieving an indoor air temperature reduction up to 15 degrees C, and provide a significant improvement of thermal comfort conditions. The environmental benefits of green roofs were focused on decreasing pollutants concentrations (e.g. PM2.5, PM10, O3, NO2), sequestering carbon and reducing urban noise.