Closing Water Cycles in the Built Environment through Nature-Based Solutions: The Contribution of Vertical Greening Systems and Green Roofs

Water in the city is typically exploited a linear process, which most of it polluted, treated, and discharged; during this valuable nutrients are lost treatment process instead being cycled back used urban agriculture or green space. The purpose paper to advance new paradigm close water cycles cities via implementation nature-based solutions units (NBS_u), with particular focus on building greening elements, such as roofs (GRs) vertical systems (VGS). hypothesis that “circular systems” can provide substantial ecosystem services minimize environmental degradation. Our method twofold: we first examine these from life-cycle point view, assessing not only inputs conventional alternative materials, but ongoing input required for irrigation. Secondly, evapotranspiration performance VGS Copenhagen, Berlin, Lisbon, Rome, Istanbul, Tel Aviv, different climatic, architectural, sociocultural contexts have been simulated using verticalized ET0 approach, rainwater runoff greywater irrigation resources. cycling mentioned would be sufficient at recycling 44% (Lisbon) 100% (Berlin, Istanbul) all accruing roof–runoff, if shortages dry months bridged by greywater. Then, 27–53% could managed its greened surface. In conclusion, address gaps current knowledge policies identified stages analyses, lack comprehensive life cycle assessment studies quantify complete “water footprint” systems.