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Greenery Promotes Efficiency, Resiliency and Public Health

Cities are home to about 50 percent of the world’s population, but they generate 80 percent of our planet’s greenhouse gases, which contribute to global warming and climate change. To reverse the destructive momentum, cities must become part of the solution.

According to architect Stefano Boeri, greener buildings can minimize the carbon footprint of cities around the world. He envisions buildings that are energy efficient and made from renewable materials. He also envisions buildings that are shrouded in greenery. He calls his concept the vertical forest.

The focus on the relationship between city and nature leads to the creation of Vertical Forest, a model of metropolitan reforestation that integrates vegetation as an essential element of architecture. The vegetation offers multiple benefits to a building, including efficiency and resiliency.

The vegetation offers multiple benefits to the building, community, city and planet.

Completed in Milan in 2014, the first Vertical Forest earned many international awards, including the International Highrise Award in 2014 and the Best Tall Building Worldwide Award in 2015 by CTBUH. Introducing the concept of biodiversity in architecture, Boeri works on the development of the Milanese model and on Urban forestry. He presented his project of Forest City in the United Nations Climate Change Conference (COP21), becoming one of the main actors in the debate on climate change in the field of international architecture.

urban forestry and global warming

“The vertical forest is a new format of architectural biodiversity,” said Stefano Boeria, founder and namesake of Stefan Boeri Architectti. “The model focuses not only on human beings but also on the relationship between humans and other living species. It brings the human and natural worlds closer together, while forging a new alliance between nature and urban buildings.”

The first example, built in Milan’s Porta Nuova area, consists of two towers that are respectively 80 and 112 meters high. They support a total of 800 trees (480 first and second stage trees, plus 300 smaller ones). It also features 15,000 perennials and/or ground covering plants and 5,000 shrubs, providing an amount of vegetation equivalent to 30,000 square meters of woodland and undergrowth, concentrated on 3,000 square meters of urban surface.

Vertical Forests can impact global land use. They can help manage urban sprawl and they can become sources of urban food production, which can minimize the need for farmland. Urban food production also minimizes the need for transportation of crops to urban areas. Each tower is equivalent to about 50,000 square meters of single-family houses.

Unlike conventional facades in glass or stone, the plant-based shield does not reflect or magnify the sun’s rays. Instead, it filters the sun. The green exterior regulates humidity, produces oxygen and absorbs CO2 and micro particles. The natural solution has earned several awards, including the International High-rise Award from the Deutschen Architekturmuseums in Frankfurt (2014) and the CTBUH Award for the best tall building in the world from the Council for Tall Buildings and Urban Habitat at Chicago’s IIT (2015).

“It seemed crazy at first”, said Manfredi Catella, CEO of COIMA, the developer of the towers and the surrounding area. “Once the towers were completed, the Vertical Forest of Milan became a landmark for the city and a symbol for world architecture.”

Once completed, the towers 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.

The towers feature large, overhanging balconies that accommodate large planters for vegetation. Larger trees have plenty of room to grow upward without obstruction. Once the vegetation fills in, the buildings resemble a pair of gigantic trees. The variations in color and shapes of the plants produce a tremendous iridescent landmark in every season.

The plants are grown in imbedded prefabricated containers. They are nourished by an irrigation system that is digitally and remotely controlled. The water is largely drawn from filtered effluent from the towers. Once a year, the flying gardeners descend from the roof of the buildings, using mountaineering techniques, for pruning.

A few years after its construction, the Vertical Forest has given birth to a habitat colonized by numerous animal species, including about 1,600 specimens of birds and butterflies.

The company has several projects around the world. In China, for example, about 80 kms from the city of Wuhan, a crane has just lifted the first tree of the Easyhome Huanggang Vertical Forest City Complex to the 25th floor. Each tower will feature 395 trees, 3,600 shrubs and 12,000 perennials. The project will be completed in February 2021.

Elsewhere in China, trees have started to reach the balconies of the towers of the Nanjing Vertical Forest, (the first Vertical Forest built in Asia by Stefano Boeri Architetti), which will host a total of 27 native plant species, 600 large trees, 200 medium-sized trees and more than 2,500 shrubs and hanging plants. The greenery will cover 4,500 square meters of surface, while contributing to local biodiversity. It also will absorb 18 tons of CO2, while producing up to 16.5 tons of oxygen every year. The first tower is 200 meters high. It is crowned by a green canopy that will creep over and down the building. The second tower will include a Hyatt Hotel with 305 rooms and a swimming pool. The two Nanjing towers will open in 2021.

In 1980, Boeri graduated in Architecture at Politecnico in Milan. In 1989, he received his PhD from Istituto Universitario di Architettura di Venezia (IUAV). As a full Professor of Urban Planning at Politecnico in Milan, Boeri has served as a guest professor at various universities, including Harvard University’s Graduate School of Design (GSD), the Strelka Institute in Moscow, the Berlage Institute in the Netherlands, and the École Polytechnique Fédérale de Lausanne. He served as designer and member of the Scientific Board at Skolkovo Innovation Center, a high tech hub near Moscow. Boeri is director of the Future City Lab of Tongji University in Shanghai. For more information, about Boeri and the vertical forest, visit

Greener Cities

Greener Cities is a division of Crossbow Communications. Greener Cities is a resource for sustainable and resilient cities and communities around the world.

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Author: Gary Chandler

Gary Chandler is a sustainability strategist, author and advocate. Follow him on Twitter @Gary_Chandler