The intensive CAM green roof at the University of Cagliari has provided several valuable lessons from its design, implementation, and long-term monitoring. The spontaneous CAM vegetation (Agave americana) has proven highly effective in Mediterranean climates, achieving a retention Index (IOR) of 0.52 without irrigation or regular maintenance. While conventional C3 vegetation can reach slightly higher retention (IOR ≈ 0.71), it requires substantial watering and ongoing care, demonstrating that CAM species offer a low-maintenance, cost-effective alternative for urban green roofs.
Continuous high-resolution monitoring of rainfall and outflow, combined with calibration of the EHSM ecohydrological model, has been essential to validate system performance. The monitoring revealed that antecedent soil moisture strongly influences retention during extreme rainfall events: dry substrate maximizes retention, whereas saturated conditions reduce available storage. This highlights the importance of considering initial soil moisture and operational strategies when designing or evaluating green roofs for stormwater management.
The roof has also demonstrated long-term viability as a self-sustaining system, with its combination of deep sandy substrate and CAM vegetation enabling effective water retention and regulation over decades, without the need for irrigation. Beyond hydrological performance, the roof provides ecological and aesthetic benefits, making it a multifunctional urban infrastructure.
Finally, the University of Cagliari CAM green roof serves as a benchmark for future innovations, such as the CAM PolderRoof, which integrates water reuse tanks while maintaining low-maintenance vegetation and high stormwater retention, showing the potential for scaling and replication in urban Mediterranean environments.