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Six years ago, Italian architect Stefano Boeri, with Boeri Studio's Gianandrea Barreca and Giovanni La Varra, completed a two-tower project in Milan’s new Porta Nuova district known as the Bosco Verticale. Translating to “Vertical Forest,” the 260- and 360-foot towers, edged by projecting concrete balconies, were covered head-to-toe with a combination of 800 trees and 5,000 shrubs.
“It seemed crazy,” says Manfredi Catella, CEO of COIMA, the developer of the towers and the area around them. “At the same time, we thought it was worth trying.”
Once completed, the towers, whose plants, nourished by an integrated irrigation system, grew out of imbedded prefabricated containers, became wildly popular, both among residents and across the city. They nested occupants in a green respite, absorbed CO2, minimized heat-island impacts, reduced energy consumption, and hosted a wide variety of plant and animal species. They also helped invigorate (along with new parks and towers by several top architects) an area that was once dominated by unused railroad tracks and decaying industrial buildings.
Although not the first-ever green-clad towers, they became a global poster child for an emerging type of architecture, covered seamlessly in plants, bringing nature to the city and calling attention to the wider green building movement. The World Green Building Council called Bosco Verticale “arguably one of the most recognizable buildings of the last decade,” while this publication has called Boeri “perhaps the most famous name in green architecture.” Catella, who points out that the towers were completed “at a moment when actively promoting the protection of nature was becoming a global need,” calls them “a world symbol uniting biophilia and urbanism as a matter of fact.”
Boeri calls the subsequent efflorescence of greenery covered buildings a “family,” which he set out to nurture and promote from the beginning. He says he never registered any copyrights for Bosco Verticale, hoping that its ideas would proliferate. “We wanted to demonstrate that this is possible,” says Boeri.
Now Boeri’s “family” is as healthy as ever. Although still the exception among new buildings, green-clad structures have sprouted (so to speak) around the world, becoming a recognized typology. Just a few notable examples include Jean Nouvel’s cantilevering One Central Park in Sydney, Vincent Callebaut’s twisting Agora Garden Tower in Taipei, Diller Scofidio + Renfro’s hybrid landscape and building complex Zaryadye Park in Moscow, and a host of vertical forests by Singapore-based WOHA, including Sky Green in Taichung, China, and the Oasia Hotel and Park Royal Tower in Singapore, with their climbing green façades, open-air sky lobbies, and balcony gardens. Ambitious new plant-clad building in the works include MVRDV’s wildly undulating “Valley” in Amsterdam and Thomas Heatherwick’s staggered, mountainous Moganshan project in Shanghai.
While legislation encouraging green roofs is now common, those calling for more holistic green surfacing are still in their early days. The undisputed leader is Singapore, where requirements and incentives assure that virtually all new buildings include plant life, like green roofs, green walls, and high-rise terraces. The government also funds up to 50% of plant installations on existing buildings. The self-described “garden city” also requires most new buildings to meet its Green Mark green certification program, and is aiming to plant one million new native trees by 2030.
Several of the world’s green-building rating systems, including the USGBC, promote the elements imbedded into vertical forests, like protection of habitats, heat island reduction, biophilic design, and rainwater management. “You’ll find an element of these types of spaces in nearly all the rating systems out there,” explains Victoria Kate Burrows, director, Advancing Net Zero, for the World Green Building Council.
Boeri’s own green-clad constructions have multiplied since the Bosco Verticale. He says he is now working on plant-covered buildings in Italy, France, Switzerland, Albania, The Netherlands, Belgium, China, and Egypt.
He’s pushing to ensure that they evolve to be greener and more efficient: He’s in early conversations with COIMA to create a mass timber framed vertical forest that would contain far less embodied carbon than what he has built to date. And he’s working on projects in Eindhoven and Utrecht in The Netherlands that utilize prefabrication to help bring costs down; making them more financially accessible.
Boeri’s next frontier is the vertical green city, which is moving ahead with Cancun Smart Forest City, near Cancun, Mexico. The 130,000 person metropolis, developed by Honduras-based Grupo Karim’s, would contain 362 acres of planted surfaces and 120,000 plants from 350 species. And with his Urban Forestry manifesto, Boeri is calling for architects, developers, scientists, and politicians to “multiply the presence of forests and trees in our cities” through vertical forests, yes, but also through tree-filled green belts, green retrofits, and urban/plant hybrid locales that he calls green jungles.
Bill Browning, cofounder of Terrapin Bright Green, an environmental consultant specializing in biophilic design, notes that COVID has only multiplied city-dwellers’ desire for green space, be it in their cities or in their homes. He adds that the benefits of plants in our living environment extend to increased focus and lowered stress response. (One of the reasons companies like Google, Facebook, and Salesforce have developed biophilic standards for their buildings.)
“Exactly,” says Boeri. “We need greenery. We need outside balconies.” And not just for humans. The Bosco Verticale, says Boeri, now hosts the nests of more than 20 species of birds, not to mention countless groups of plants, who he considers the primary tenants of the building. He has a particular soft spot for the trees. “I’ve always been obsessed with trees,” he says. “They are individuals, they have their own evolution and trajectory and intelligence and sensibility.”
