GREENO2 research on the hydrological performance of a modular Blue–Green Roof (BGR) has been accepted for presentation at the Green Building 2026 International Scientific Conference, which will take place on 15–16 October 2026 in Niš, Serbia. The conference, organised by the Faculty of Civil Engineering and Architecture of the University of Niš, focuses on innovative solutions for a greener built environment and brings together researchers, PhD students and professionals working on sustainable and climate-resilient approaches to the built environment.

The research, entitled “First-Year Monitoring of the Hydrological Response of a Modular Blue–Green Roof under Mediterranean Climate,” was carried out by researchers from the University of Tuscia (Viterbo, Italy): Prof. Andrea Colantoni, Prof. Andrea Petroselli, Prof. Raffaele Pelorosso, Prof. Ciro Apollonio, Prof. Flavia Tauro, Prof. Francesco Cappelli and Prof. Salvatore Grimaldi. The study was conducted within the framework of the Erasmus+ GREENO2 project – Green Roofs in Higher Education Institutions as Sustainable Centers for Research, Participation, Environmental Awareness and O2 Generation.

Monitoring a Blue-Green Roof in Central Italy

Blue-Green Roofs represent an evolution of conventional green roof systems, combining vegetation and growing substrates with engineered water-retention and detention layers. This integrated design can contribute to improved stormwater management while providing wider environmental benefits.

The study presents the first-year monitoring results of a full-scale modular Blue–Green Roof installed at the University of Tuscia in Central Italy. The system was continuously monitored from July 2025 to June 2026, using high-resolution measurements of precipitation, runoff and substrate volumetric water content.

The research focused on the seasonal hydrological response of the roof, particularly its capacity to retain rainfall and the dynamics of water stored in the substrate.

75% of Annual Precipitation Retained

During the monitoring period, the Blue–Green Roof received 1,017.8 mm of precipitation, while generating only 255.2 mm of runoff. This corresponds to an annual Retention Index of 0.75, meaning that approximately 75% of the precipitation was retained by the system during the first year of monitoring.

The results also revealed clear seasonal variation. The highest retention efficiencies were recorded during spring and summer, while lower values were observed during the wetter winter months. Continuous monitoring of substrate volumetric water content further demonstrated the influence of Mediterranean climatic conditions on the roof’s hydrological response.

Nature-Based Solutions for Sustainable Buildings

The findings demonstrate the potential of modular Blue-Green Roofs as Nature-Based Solutions (NBS) for reducing rooftop runoff and improving the hydrological performance of sustainable buildings.

Beyond the first-year results, the monitoring programme provides an important experimental dataset for future performance assessment, hydrological modelling and the optimisation of Blue-Green Roof design under Mediterranean climatic conditions.

The research contributes directly to the objectives of the Erasmus+ GREENO2 project, which promotes green roofs as multifunctional spaces that can support environmental sustainability, research, education and awareness in higher education institutions.

The presentation of these findings at Green Building 2026 International Scientific Conference will provide an opportunity to share the GREENO2 research with an international scientific audience and contribute to the wider discussion on sustainable construction, climate resilience and innovative Nature-Based Solutions.

Research title: First-Year Monitoring of the Hydrological Response of a Modular Blue–Green Roof under Mediterranean Climate

Authors: Andrea Colantoni, Andrea Petroselli, Raffaele Pelorosso, Ciro Apollonio, Flavia Tauro, Francesco Cappelli and Salvatore Grimaldi

Institution: University of Tuscia, Viterbo, Italy

Conference: Green Building 2026 – International Scientific Conference

Date: 15-16 October 2026

Location: University of Niš, Niš, Serbia

The full text of the scientific publication is available below.