Plenty of towerblocks these days claim to be ‘green’, yet few fit the criteria quite like Bosco Verticale. Literally translating as ‘vertical forest’, Milan’s Bosco Verticale exterior is covered with more than 900 trees, 5,000 shrubs and 11,000 floral plants, covering 96,000 sq ft of terraces.
The project is the creative vision of architect Stefano Boeri, known for his work creating urban forests. Also behind this naturally pollution-eating building are landscape architects Studio Emanuela Borio and Laura Gatti, and structural engineers Arup.
How the vertical forest was built
The engineering team worked with botanists and horticulturalists to find the right plants for the building’s exterior. It took 2 years of observation to determine the most resilient species. These plants were then tested in a wind tunnel to ensure the trees would not topple from gusts of wind. The largest trees most exposed to wind have a safety steel cage that restraints the root-bulb and prevents it from overturning under major windstorms. Meanwhile, the concrete balconies are steel-reinforced designed to be 28cm thick, with 1.30m parapets.
Bosco Verticale sits above the Milan Metro system, so Arup had to consider ways to help mitigate the effects of the existing underground tunnels. Vibration surveys and in-situ tests to allow analysis of the structure took place during construction. Design solutions were installed to counteract the effects of the 2 existing railway tunnels by means of a vibration base-isolation system for the main buildings.
The unique design of the towers required a customised formwork and scaffolding concept, provided by manufacturers PERI. The concept included a rail climbing system, PERI UP scaffold system and SKYDECK panel slab formwork.
Using plants to fight pollution
The 20,000 trees and plants in the buildings convert as much as 44,000 pounds of carbon each year. The plant life is used to moderate temperatures in the building in the winter and summer, by shading the interiors from the sun and blocking harsh winds. The vegetation also protects the building and its inhabitants from noise pollution and dust.
The building itself is self-sufficient by using renewable energy from solar panels and filtered waste water is used to irrigate the building’s greenery. These systems means the twin towers of Bosco Verticale have vastly reduced its overall waste and carbon footprint.
Should we adopt more vertical forests?
Bosco Verticale was designed as part of the rehabilitation of a wealthy district of Milan at a cost of nearly £49m, meaning vertical forests are not an obvious choice for an affordable housing solution.
However, architect Boeri has agreed a partnership with Dutch housing association Sint Trudo to bring his urban forest to a new social housing development in the city of Eindhoven for low-income residents.
Boeri says: “The high-rise building of Eindhoven confirms that it is possible to combine the great challenges of climate change with those of housing shortages. Urban forestry is not only necessary to improve the environment of the world’s cities but also an opportunity to improve the living conditions of less fortunate city dwellers.”