Enzi, V., Manso, M., Aires, A., Almalla, R.,Catalano, C., Elkadi, H., Emilsson, T., Heysham, N., Kroes, S., Gedge, D., Grant, G., Ribotta, L., Spaan, K., Suonio, T. and Van Roosmalen, P. Editors: Vierikko, K., Orta-Ortiz, M.S., Nieminen, H., Vasilakopoulos, P., Velasco Gomez, M.
Abstract
This report is the response to a policy request submitted by DG Environment to the EC Knowledge Centre for Biodiversity (KCBD) through the KCBD ticketing system. KCBD assigned this to the BioAgora project, to be answered by the Science Service for Biodiversity (SSBD).
Green roofs and green walls are proven, scalable solutions for restoring nature in cities, while delivering measurable benefits for climate resilience, biodiversity, energy efficiency, and human well-being. Evidence from case studies across Europe shows that extensive green roofs dominate current implementation, while intensive roofs and vertical greening systems offer higher biodiversity and social value when supported by appropriate design, governance and maintenance. Monitored sites report significant cooling-energy savings, stormwater retention, and support for hundreds of species, particularly pollinators and birds. Results highlight that performance depends on system typology, vegetation diversity, structural complexity, and integration within wider urban green networks, as well as on hybrid governance models combining public leadership with private and community engagement. Participatory approaches, biodiversity monitoring, and multifunctional strategies remain underused but represent major opportunities to increase effectiveness, acceptance, and long-term impact.
This knowledge synthesis report directly supports the implementation of the EU Nature Restoration Regulation and related climate, biodiversity and urban policies, by providing actionable guidance for local authorities and urban planners to meet urban restoration targets through building-integrated greenery.
Foreword
In April 2025, DG Environment submitted a policy request to the Knowledge Centre for Biodiversity (KCBD) through the KCBD ticketing system, for a synthesis of the current state of knowledge on best practice in the design, installation, and maintenance of green roofs/walls for residential and commercial use in Europe. The KCBD assigned this task to the Science Service for Biodiversity (SSBD), which is currently being developed by the BioAgora project. The SSBD is being developed to bridge research outcomes with decision-making needs.
Acknowledgements
Process Coordination and Facilitation
This knowledge synthesis was coordinated by the BioAgora project, which is funded by the Horizon Europe programme. The request handling and expert coordination were overseen by:
Request Focal Points & Editors: Kati Vierikko (Finnish Environment Institute – Syke), M. Susana Orta-Ortiz (University of Trento) and Hanna Nieminen (Finnish Environment Institute – Syke)
Coordination Period: 23/04/2025 – 24/02/2026
The focal points served in a coordination and process facilitation capacity, ensuring adherence to ethical standards, facilitating communication between the expert working group and requesters, overseeing the peer review process, and maintaining the integrity of the knowledge synthesis methodology. Their role was specifically designed to support the independence and objectivity of the expert working group while ensuring procedural rigor and transparency.
KCBD Contact Points & Editors: Paris Vasilakopoulos (JRC.D6) and Marcela Velasco Gomez (EC consultant)
DG ENV Contact Point: Benjamin Rolles (ENV.D2)
Expert Contributors
Authors
Vera Enzi (co-lead, European Federation of Green Roof & Living Wall Associations – EFB, Austria)
Maria Manso (co-lead, Universidade Lusófona, Portugal)
Alessandra Aires (Turin City Council, EU and Innovation Department, Italy) Rima Almalla (University of Turku, Finland)
Chiara Catalano (Italian National Research Council, Italy) Hisham Elkadi (Salford University, England)
Tobias Emilsson (Swedish University of Agricultural Sciences, Sweden) Nourhan Heysham (University of Manchester, England)
Simone Kroes (Climate Adaptation Services, The Netherlands)
Dusty Gedge (Independent green roof and urban biodiversity professional, UK) Gary Grant (Green Infrastructure Consultancy, UK)
Laura Ribotta (Turin City Council, EU and Innovation Department, Italy) Kasper Spaan (Waternet Amsterdam’s s water utility, The Netherlands) Taina Suonio (Roslings Manor Gardens, Finland)
Paul van Roosmalen (City of Rotterdam, The Netherlands)
Reviewers: Jürgen Preiss (City of Vienna, Austria) and Elena Comino (Politecnico di Torino, Italy)
Conflicts of Interest and Independence
All expert contributors, methods experts, and focal points completed conflict of interest declarations. The focal points did not contribute to the substantive content of this output to maintain process independence and objectivity, while the methods expert participated as a full member of the expert working group with full intellectual contribution rights. Complete conflict of interest documentation is available upon request.
Contributions to this output are recognized through:
⎯ Clear citation and attribution in all produced documents
⎯ Formal acknowledgment provided to all contributors by DG Environment
⎯ Integration of contributor recognition in Science Service communications and publications
⎯ Feedback mechanisms to inform contributors about the use and impact of their contributions.
The focal point review found no conflicts requiring management beyond disclosure. Panel membersbring complementary institutional perspectives – industry association knowledge of market dynamics,
municipal implementers’ understanding of regulatory contexts, research experience with long-term ecological monitoring, and consulting expertise in practical implementation. These diverse
positionalities enriched the synthesis while remaining within appropriate bounds for independent assessment. The panel composition prioritized technical and ecological expertise consistent with the synthesis objectives.
Disclaimer
The views expressed in this output represent the collective assessment of the expert working group based on available evidence. The coordinating focal points and supporting institutions do not endorse specific recommendations but have ensured adherence to transparent and rigorous process standards.
For questions regarding the coordination process or to provide feedback on this output, please contact: kati.vierikko@syke.fi
Executive summary
Policy context
This report is the response to a policy request submitted by DG Environment to the EC Knowledge Centre for Biodiversity (KCBD) through the KCBD ticketing system. KCBD assigned this to the BioAgora project, to be answered by the Science Service for Biodiversity (SSBD). The report supports the Nature Restoration Regulation by showing how building-integrated vegetation systems, such as green roofs and green walls, can help meet urban greening targets. Drawing on experiences from different European climatic regions and prepared by a multidisciplinary team of experts assembled by BioAgora, it offers insights into system types, suitability, installation and maintenance needs. The report highlights governance challenges, economic aspects and key environmental and social benefits. It provides actionable guidance for local authorities and urban planners to support informed decisions and strengthen the installation of green roofs and green walls across the EU.
Key conclusions
This report confirms that green roofs and green walls are strategic nature-based solutions (NbS) that can support cities in delivering multiple objectives under the Nature Restoration Regulation, the EU Biodiversity Strategy, climate adaptation frameworks, and related urban policies. Evidence from European case studies shows that building-integrated greenery can deliver measurable benefits for biodiversity, climate adaptation, stormwater management, energy efficiency and social well-being, validating core assumptions behind current policy approaches. However, implementation across Europe remains uneven, constrained by regulatory fragmentation, financing and maintenance challenges, skills gaps, and limited integration into mainstream planning and building practices.
To address these barriers, the findings point to the need for systematic policy integration, embedding green roofs and walls into spatial planning instruments, and building codes and incentive schemes with biodiversity and climate-resilience criteria.
Policy options emerging from the analysis include strengthening planning and building regulations, introducing targeted incentives and funding schemes, embedding biodiversity-oriented design and monitoring requirements, and promoting multifunctional green roofs and walls that combine greening with renewable energy, water management, and social functions. Performance-based planning tools — such as green space and rainwater management factors, and multifunctionality scoring systems — offer effective mechanisms to guide investment, prioritise co-benefits and support transparent decision-making.
Long-term performance depends on adaptive management, underpinned by biodiversity- oriented maintenance regimes, Internet of Things (IoT)-enabled monitoring and biodiversity tracking, and
meaningful citizen and stakeholder engagement. Municipalities play a central role in this transition, requiring strengthened cross-departmental coordination and vertical integration across
governance levels.
The report also highlights opportunities for innovation and cross-sector collaboration, particularly through solutions that link energy, water, circular material use and biodiversity objectives, presenting current trends and participatory governance models that can accelerate scaling and cost-effectiveness. Simulation tools and remote sensing data can support decision-making and cost-benefit optimization.
This knowledge synthesis significantly reduces uncertainty by consolidating practical evidence and transferable lessons, providing a stronger basis for informed, action-oriented policymaking giving
recommendations on key actions on holistic design, local adaptation, stakeholder engagement, innovation, and knowledge transfer.
Introduction
1.1 Background and policy context
European cities face increasing environmental pressures driven by climate change, biodiversity loss, urban densification, and expansion. In this context, building-integrated vegetation systems — particularly green roofs and green walls — are gaining recognition as a valuable category of nature-based solutions (NbS) that can enhance urban resilience, support biodiversity, reduce heat stress, and contribute to more livable urban environments.
A broad set of EU and international policy frameworks converge to support the implementation of green roofs and walls across Europe. At the center of this policy landscape is the Nature Restoration Regulation (NRR), which establishes clear requirements for expanding and improving urban green spaces.
The EU Biodiversity Strategy for 2030 reinforces the need to enhance ecological connectivity and reverse nature loss in cities, goals directly aligned with the habitat provision and pollinator support afforded by vegetated roofs and walls.
Although these systems primarily contribute to the NRR, particularly Article 8 on urban ecosystem restoration, their relevance extends across multiple policy domains, reflecting the inherently cross-cutting nature of building-integrated greenery, for example:
⎯ Energy Efficiency Directive (EED) and Energy Performance of Buildings Directive (EPBD): These frameworks recognize the value of building-integrated and building-adjacent vegetation systems for their local microclimatic effects, such as reducing urban heat islands. They also highlight the direct impact of such systems on building energy efficiency, lowering cooling and heating demand, and welcoming the integration with solar, thereby influencing energy certification processes and the development of a Building Renovation Passport (BRP).
⎯ Urban Wastewater Treatment Directive (UWWTD): This directive emphasizes water-sensitive design at both plot and neighbourhood scales, positioning building-integrated NbS as a key component of wastewater strategies. Such measures provide water purification services, prevent urban flooding through on-site capture, and contribute significantly to the formulation of Urban Wastewater Plans.
Green roofs and walls offer practical, scalable solutions to help cities meet these obligations, especially where ground-level space is limited. Surrounding this core policy (NRR) are several complementary EU strategies and directives that collectively strengthen the case for widespread adoption. Meanwhile, the EU Climate Adaptation Strategy highlights NbS as essential components of resilient urban design, recognising their ability to reduce heat stress, manage intense rainfall, and mitigate flood risks.
In addition to EU legislation, national and municipal initiatives across Europe demonstrate how governance and regulatory innovation can accelerate the implementation of green roofs and green walls. Examples include mandatory green roof and wall requirements in cities such as Basel, Vienna and Berlin, financial incentive schemes at national or regional level, and urban development plans that incorporate ecosystem-service considerations. These policies illustrate the diversity of approaches available to Member States and offer practical models that can be adapted to local contexts.
Taken together, these policies form a multi-layered enabling environment that supports the integration of building-integrated greenery into urban planning and development. This report
underscores that green roofs and walls are not only restoration measures but also strategic assets that advance EU ambitions in climate resilience, biodiversity recovery, energy efficiency and
public health. This alignment of policies provides a strong foundation for Member States and cities to scale up implementation, ensuring that green infrastructure becomes a standard element of
Europe’s sustainable and resilient urban future. Further guidance for national stakeholders is both provided and needed, as the overall impact strongly depends on the coherent national adaptation of
current policies and regulations, starting with the EED and EPBD (Enzi‑Zechner, 2026).
1.2 Purpose of the report
This report has been prepared to synthesize available knowledge and practical experience on the implementation of green roofs and walls across Europe. Its purpose is to inform EU, national and local authorities as they design and implement restoration measures and urban greening strategies aligned with EU policy objectives.
The study was prepared for the European Commission, in collaboration with BioAgora and a multidisciplinary team of experts, including scientists, designers, local authorities and non-profit organisations, ensuring comprehensive practical insights.
The main goals of this report are to assess current practices and experiences with green roofs and walls across different European climatic regions, providing an overview of the different system types, their technical characteristics and suitability for different building contexts (e.g. residential, commercial, new build or retrofit), including their combination with other technical features (e.g. solar panels). Also, it aims to identify key enablers and barriers for implementation related to their installation, maintenance, governance frameworks, and economic viability. In sum, this report synthesizes the lessons learned from European examples to support policy design and practical implementation, giving actionable guidance to local authorities, urban planners and policymakers to support informed decision-making and accelerate the implementation of building-integrated greenery.
1.3 Problem and significance
The central challenge addressed by this report is the limited and uneven deployment of green roofs and walls across European cities. Although the environmental and social benefits of these systems
are well-documented, many cities face gaps in technical knowledge, regulatory support, financing mechanisms, and long-term maintenance planning. Overcoming these barriers is essential for
achieving the urban ecosystem restoration targets defined in the NRR and for advancing wider EU climate and biodiversity goals.