The desired green city that Barcelona should transform into is a shared responsibility to which each and every Barcelonian can contribute. Any action is welcome if it improves the environment.
Meanwhile, in parallel, administrations promote measures in the same direction. Some of them spur citizens to become aware that their participation is essential and that there are many resources that can be leveraged. The only things needed are will and determination—and a small economic effort, perhaps—.
Precisely these circumstances and the tenacity of a group of residents of Avenida Diagonal, in Poblenou, have made it possible to convert the rooftop of their apartment building into a garden and green recreation area. A green lung in the city's urban landscape. Now the space is one of Barcelona's most splendid green roofs.
The building is a reference for National Geographic, which has reported on it in a feature about neighborhood initiatives versus urban sustainability, and it was one of the projects chosen in 2020 in the second green roof competition organized by the Barcelona City Council, through the Municipal Institute of Urban Landscape.
It should be noted that the 55 residents of the Diagonal building do not fit a single resident profile, but they did show a certain interest in environmental respect due to the fact that they acquired their homes in a development that already incorporated photovoltaic panels on the rooftop from the outset and were willing to share spaces such as the communal pool.
At the same time, they were aware that reaching the top of the building offered them privileged views of the city, the Collserola natural park, and the central park of Poblenou. But using the rooftop caused certain inconveniences to residents of the upper floors due to the noise generated and some waterproofing problems. In short, a solution needed to be found.
It was 2018 when all this was happening and when the Barcelona City Council had launched what was the first green roof competition in the city. With this measure, Ada Colau's government team got to work on a proposal that had been around for much longer, since 2014, when then-mayor Xavier Trias made a plan for living rooftops and green roofs in municipal and private buildings so that the rooftops would also recover their old spirit of coexistence.
"It was a series of coincidences that pushed us to reflect, to look for solutions," explains Jordi Sumalla Llobera, a resident and president of the community of owners of the Poblenou property. Some of the residents, like himself, are clear defenders of the fight against climate change and knowing that there was the option of building a green space on the rooftop for the enjoyment of the community, "we didn't think twice". "It was an idea that had been buzzing in our heads and that, moreover, became an urgent necessity when months later we were confined by the pandemic," he adds.
With the tenacity of the group of neighbors, "we launched ourselves." "Let's admit it's not an easy task," he explains, reviewing the various neighborhood meetings ---"some endless and nocturnal," he comments--- that were necessary to finally obtain the support of 60% of the owners; necessary to carry out the project.
The project had the support of 60% of the owners of the 55 homes in the building"But everything was carried out in the most democratic way possible, with the opening of a participatory process to design the roof, modify some of its characteristics if necessary, choose its uses, define accessibility, evaluate the costs of realization and, above all, of maintenance... until achieving a plan that excited everyone." The project took its definitive form and was presented on May 25, 2020, in the second green roof competition of the Barcelona City Council, and was one of the ten selected.
As Jordi Sumalla explains, this was a great help because then a subsidy of 1,500 euros is obtained for technical expenses of the competition phase, which covers initial costs and 75% of the total value of the action and technical studies necessary to carry out the work, up to a limit of 100,000 euros. However, while waiting for public money to arrive, the community has taken out a three-year loan with Caixa Guissona, a cooperative entity committed to the environment, sustainability, and the fight against climate change, and "which has not put any obstacles in our way, quite the opposite," he states.
The neighborhood leader recalls how they attended the open days held on some of the rooftops that had already been transformed in the city and how they put themselves in the hands of EixVerd, a social enterprise, with a shop on Bailèn street, which promotes the sustainability of urban centers with adaptation and mitigation projects for climate change. They also collaborated with Mataaltastudio and a team from the Universitat Politècnica de Catalunya (UPC) for the re-naturalization design of the rooftop. "And, finally, we made it a reality between October and December 2021," says Sumalla.
The founder and director of EixVerd, Lidia Calvo, acknowledges that reaching a consensus on the transformation of rooftops is not an easy task: "Of the proposals we receive, only between 5% and 10% end up materializing," but not due to structural problems of the properties, but due to the lack of consensus among owners and neighbors. Although she admits that currently "it seems that interest in this type of action has reawakened."
In most of Barcelona's rooftops, a green space could be opened, with different thicknesses depending on the age of the structure and architectural conditions, in addition to complying with a minimum of municipal regulations, "because to cultivate some of the Mediterranean climate plants, ten centimeters of soil are enough." The Barcelona City Council itself points out that 67% of the city's roofs are rooftops, that is, flat and generally accessible roofs ---which correspond to 1,700 hectares, equivalent to an area comparable to twice the surface of the city's Eixample---, and that 20% also have optimal characteristics for solar energy use.
In the case at hand, EixVerd has designed the Diagonal rooftop with different substrate thicknesses in order to obtain a variety of plants, from herbaceous to shrub areas that enhance biodiversity; there are rest areas and an insect hotel, it also has night lighting, among other features. The final cost: 133,000 euros.
The maintenance of this green space costs 50 euros per year per dwelling and includes 18 visits throughout the year by EixVerd technicians who check the ditch, fertilization system, prune, check the hydraulic system... Calvo assures that it is in line with the cost of maintaining a green roof in the city, and he knows this for a fact, because they have built more than twenty, totaling more than 10,000 square meters of surface area.
The average cost to landscape a rooftop ranges between 100 and 300 euros per square meterThe price of projects varies depending on the elements incorporated into the roof, whether due to the ornamentation of the space, the type of vegetation, irrigation tools or tanks to take advantage of rainwater, electrical connections; "but, ultimately, we always talk about between 100 and 300 euros per adapted square meter."
Considering that Barcelona is a compact city with high residential density and a deficit of green spaces, rooftops are a great opportunity. As are urban gardens or party walls and the naturalization and permeabilization of blind fences and the conversion of unbuilt spaces into permeable and landscaped areas. All of these are key elements to achieve a greener and more sustainable city, as established by the Barcelona Green and Biodiversity Plan 2020 and the Urban Green Infrastructure Promotion program.