Creation of green roofs and walls

The project focused on implementing multilayer blue-green roofs in four Italian cities—Cagliari, Palermo, Perugia, and Viterbo—as part of a broader European initiative to address climate change impacts in urban environments (1,3). Spearheaded by a collaboration between multiple Italian universities and the Dutch company Metropolder, the project began in 2019 (1,3). The primary goal is to enhance urban resilience by integrating green infrastructure capable of mitigating climate-related urban hazards such as flooding and heat waves, which are increasingly severe due to climate change and urbanisation (2,3).
The multilayer blue-green roofs combine the ecological benefits of traditional green roofs with an added water storage layer, allowing them to retain rainfall and manage runoff effectively (2,3). This dual function helps reduce pluvial flooding and the urban heat island effect, while also improving thermal insulation in buildings (2,3). Each installation was planted with low-maintenance, climate-adapted vegetation, and equipped with sensors to monitor ecohydrological and thermal performance over several years (1,3). These roofs are capable of retaining up to 100% of rainfall from significant events, thereby easing the burden on urban drainage systems and contributing to climate adaptation in Mediterranean cities (2,4).

On the site of a former malthouse in Berlin, a company has developed a sustainable rainwater storage system to prevent flooding in the sealed environment, which had been vacant for several years. Once used for malt production, the site is now home to offices, studios, manufacturing businesses, and hosts sustainable events. The site's transformation includes natural gardens, tenant gardening beds, green roofs, and two outdoor water basins that retain rainwater, creating a blue space for recreation. (Ref. 1)
The two ponds are filled with filtered rainwater, and an underground tank stores additional water, allowing it to seep away gradually. Native plants surround the ponds, creating a habitat for local wildlife. Given that much of the surrounding area is sealed, the ponds help mitigate urban flooding by managing and storing rainwater, reducing the site's reliance on the urban sewage system. Additionally, as Berlin faces extreme heat in summer, the project offers a cooling effect and provides access to filtered water during droughts. (Ref. 1; Ref. 2)
The project is managed and financed by IGG Malzfabrik mbH, which oversees the entire site in Berlin's industrial area and rents out office spaces to various companies. This initiative is part of a broader sustainability strategy that addresses social, economic, and ecological factors, and it is featured in the company’s common good economy report (Gemeinwohl-Ökonomie Bericht). (Ref. 5)

The Torre Sevilla is a commercial building complex with extensive green roofs. The green roofs cover 11000 or 12000 m2 (different sources report different numbers) and aim to contribute to thermal isolation and energy efficiency of the building, improve air quality and provide an urban green space for relaxation and recreation [Ref. 1-3]. The green roofs include a mosaic of different vegetation types and about 60 mostly native plant species. There is a rainwater recovery system that allows the gardens to be irrigated in a sustainable way [Ref. 1-3, 6]. The building finished construction in 2017 and the gardens were initially not available to the public. In 2023, the owner applied for a permit to host events in the gardens, which will allow the public to visit on occasion [Ref. 1, 3-5].

The Ringsend Open-Air Laboratory project in Dublin, Ireland, is part of a broader effort to adapt urban areas to increasing climate change risks. This initiative focuses on installing green roofs and deploying a network of environmental sensors to enhance urban resilience. Launched in 2018 under the Horizon 2020 OPERANDUM project, the effort seeks to find nature-based solutions for climate change impacts worldwide. Led by the University of Bologna, OPERANDUM involves over 20 partners, primarily in Europe, working together to address environmental challenges like flooding, drought, and coastal erosion through the establishment of ten "Open Air Laboratories" globally.
In Dublin, the project aims to bolster flood resilience in Ringsend, a critical economic area near the city’s tech district, which faces substantial flood risks due to its low elevation and proximity to the Dodder River. This river, which flows through both rural and urban areas before meeting the River Liffey near Ringsend, has caused property and infrastructure damage from extreme rainfall and combined river and tidal flooding.
Green roofs play a key role in mitigating urban flood risks in this project. These rooftop gardens absorb large volumes of rainfall before it reaches the streets, easing the load on existing flood prevention systems like storm drains and gullies and reducing the need for additional "grey" infrastructure. Based on community insights and recommendations, construction has begun on a green roof on top of the CHQ building in Dublin’s Docklands, in partnership with Dogpatch Labs.Complementing this, over 100 sensors have been deployed in recent research trials across Dublin. OPERANDUM researchers are now building on this foundation to create a denser, more reliable, and cost-effective sensor network, with data from earlier low-cost sensor trials made publicly accessible via Dublinked, Dublin’s open data platform, and exploring the use of LPWAN for environmental sensing. (1-5, 7)

The Institute of Physics at Humboldt University of Berlin is an outstanding example of ecological urban development and a global pilot project integrating rainwater management with building cooling through greening. A key feature is the cooling system, which relies on air circulation processes supported by green roofs, facades, and an artificial wetland/pond incorporated into the building's exterior and courtyard.
Rainwater is collected in cisterns and used to irrigate the green façade, enabling evaporative cooling in air conditioning systems. Excess water is either evaporated in the inner courtyard through a pond or allowed to seep away. (Ref. 1; Ref. 4) The greening of the façade is directly linked to energy optimization. During summer, the green façade provides solar shading against extreme heat, while in winter, sunlight passes unobstructed through the glass façade. Additionally, evaporative cooling improves the microclimate inside the building and its surroundings. (Ref. 3)
Berlin, as a densely built city, faces challenges like urban heat and high energy demands for cooling. This project offers a research-driven solution. Monitoring measures water usage for various plants, evaluates evaporative cooling effects, and assesses impacts on the building's energy balance and overall economic and ecological performance. The findings aim to create a foundation for the long-term implementation of innovative, cost-effective technologies. This process is conducted by multiple regional universities. (Ref. 1)
The project was initiated and financed by the state of Berlin and implemented after the building's construction. (Ref. 4; Ref. 5) It serves as a benchmark for sustainable urban development and a research model for similar initiatives worldwide.

The Alexandria Governorate is especially susceptible to the impacts of climate change, a vulnerability exacerbated by its dense coastal communities and rapidly growing population (2). Both demographic shifts and urban development intensify how climate phenomena affect the people and infrastructure of Alexandria (1). Buildings, roads, and other concrete structures absorb and release solar heat, significantly contributing to the urban heat island effect, which is causing temperatures in the city to rise faster than in less developed areas (1). Despite Alexandria’s growing need for cooling green spaces, they currently make up only 0.25 percent of the total area within the Governorate, highlighting an urgent need for environmental interventions (3-6).
In response, Ahmed Gaber, chairman of the Alexandria Water Company, initiated a public awareness campaign in 2023 focused on the numerous benefits of planting green roofs (3-6). Green roofs serve multiple purposes: they extend the longevity of buildings, lower energy consumption, improve air quality, increase biodiversity, manage rainwater runoff, and mitigate the urban heat island effect (3). Furthermore, Gaber has emphasized the visual appeal of eco-friendly roofs, noting that green roofs offer an aesthetically pleasing option that enhances the urban landscape while serving critical environmental functions (4).
This initiative by the Alexandria Water Company marks a pioneering step among governmental organizations in the region, as they lead efforts to address climate and environmental challenges actively. The company has begun planting green roofs across its facilities, including the new Al-Mashishya water station, where green spaces atop buildings are set to bring lasting environmental benefits to Alexandria. Through these efforts, the Alexandria Water Company is working to set an example for public and private sectors alike (3-6).

In an architecturally important area of Berlin, situated between the Landwehr Canal, the Kulturforum (the Berliner Philharmonie and the Berlin State Library) and the new construction on Potsdamer Platz, a combination of green and grey infrastructure has been realised to minimise the burden on Berlin’s existing water infrastructure.
Green and non-green roofs harvest annual rain, which flows through the site’s buildings and is used for toilet flushing, irrigation, and fire systems. The roofs retain and then release water to the large on-site buffer pond, which has five underground storage tanks. Next to the roofs, a series of urban ponds and connecting canals have been implemented, with a combined area of approximately 1.2 hectares. They are filled with rainwater, creating an oasis for urban life. Vegetated biotopes are integrated into the overland landscape and serve to filter and circulate the water that runs along streets and walkways. The lake’s water quality is excellent, forming a natural habitat for animals and cooling the surroundings, while fresh water usage in the buildings has been reduced. (Ref. 1; Ref. 2; Ref. 3; Ref. 6)
The project was implemented in the 1990s as part of the development of Potsdamer Platz in the wake of the reunification of Germany. Several architects collaborated on the implementation that was completely privately funded. Beyond its ecological and technical features, the site is a blue natural site in the heavily built city centre of Berlin and allows people to linger and enjoy natural features. The drainage system won several sustainability prices and is considered a successful integration of nature and technology-based mechanisms to foster climate change adaptation. As the rainwater system stores rainwater in underground tanks and ponds, the urban sewage system is relieved during heavy rain, and water can evaporate. Therefore, the small water circle is closed, and the microclimate is cooled. (Ref. 2; Ref. 6)

Located in the Lima district of San Isidro - the heart of commercial activity in Peru - the Real Dos Tower is a prime office building in the Centro Empresarial Real de San Isidro. It was inaugurated in 2018, and it is distributed over 23 levels (14 floors and 9 basements) and enjoys a landscaped green roof (1162 m2) at the crown of the building and numerous outdoor vertical gardens at full height (2365 m2) on the three main fronts (1, 4). This project was a finalist in the 2018 Mipim Awards, considered the ‘Oscars’ of world architecture, and stood out for its architecture and design, due to its attributes of innovation and sustainability (2).
This building has managed to create harmony between design and efficient use of resources. It is characterised by a glass façade with colourful movable shutters and symbolic Peruvian designs (2, 3, 6). It has green walls on the three main fronts, four daylight fronts and a roof garden (2). The architect, Jean Nouvel, worked together with ARVE Peru on the overall landscape plans for the Real Dos tower (1, 3).
This is part of the façade remodelling project of the Camino Real Towers in the Real Business Centre, led by the real estate company Grupo Centenario (1, 2, 3, 4, 5, 6). This overarching Project has sought to develop 4,475 m2 of vertical gardens and roof gardens, which have a technified irrigation system to generate efficiencies in water use, meeting the plants' water requirements in the different seasons of the year. Their implementation helps to filter CO2 and renew the O2 in the office complex.
The ARVE group describes these actions as conducive to creating thermal barriers and sound insulation, a better environment for rest, work and entertainment and increasing property value (7)

Biotope City Wienerberg is located in the southern part of Vienna on a 5.4-hectare site that once housed a Coca-Cola factory. It lies at the edge of the Wienerberg recreational area, surrounded by business parks and tower blocks to the west and predominantly detached houses to the east (Ref. 1).
The project embodies the concept of an "urban biotope" (Ref. 2), grounded in the principle that nature's mechanisms of self-regeneration are essential for mitigating the challenges of urban living and climate change. By integrating urban and natural spaces, Biotope City fosters both human-nature connections and social interactions through activities like community gardening. The project’s centerpiece is its extensive green infrastructure, including trees and green roofs, which serve to cool the microclimate, purify the air, enhance water retention, and create carbon sinks while providing habitats for local wildlife. These green spaces aim to improve physical health through cooling effects on hot days and support mental well-being with their calming influence (Ref. 1; Ref. 2).
Biotope City encompasses:
Around 980 flats, including 400 subsidized flats and 200 SMART flats
A school, a kindergarten, and 2,000 square meters of children's and youth playgrounds
600 square meters of community gardens and 3,850 square meters of ground-floor gardens
250 trees, 8,900 square meters of meadows, and 13,600 square meters of green roofs
2,200 square meters of façade greening
The inner courtyards and roof areas are designed for gardening, while façades are greened, and balconies are equipped with integrated plant troughs. Even the spaces between buildings are climate-effective, featuring unsealed catchment and seepage areas to manage water sustainably (Ref. 1).
The project’s implementation took 18 years and involved collaboration among various stakeholders. The concept was initiated by the Biotope City Foundation and funded by eight different investors (Ref. 2).

The Tirana Vertical Forest is part of the city's 2030 Master Plan and aims to enhance urban biodiversity and create green spaces through innovative urban design (Ref. 1,2). The project was developed by Stefano Boeri Architetti, the same studio that has designed similar, well-known structures in cities like Milan, Utrecht and Nanjing (Ref. 6). The completion of the 21-floor building is expected in late 2024 and will feature 105 apartments and a commercial ground floor as well as 145 trees and over 3,200 shrubs and bushes which are integrated into the balconies and façade of the project (Ref. 1,2,3). Various Mediterranean plants have been incorporated, including colourful, scented and aromatic types, which harmonize with the local ecosystem. To maximise the space available for green features, a dynamic structure with alternating balconies and full-height windows has been built (Ref. 1,2). Ultimately, the project anticipates improving air quality, reducing noise, and providing insulation. The greenery is expected to capture fine particulate matter and up to 8 tones of Co2 per year while also creating a healthier microclimate for those inside the building (Ref. 1,6).