Project: Bosco Verticale
Jodie Jones discovers the design details behind the iconic vertical forest in Italy
The Bosco Verticale in Milan, begun in 2009 and completed in October 2014, was created by biological architect Stefano Boeri as a response to concerns about the environmental survival of contemporary European cities.
“This is an approach to metropolitan reforestation that contributes to the environment and biodiversity without expanding the territory of the city,” he explains.
The Bosco Verticale takes the concept of a living wall to its ultimate extreme. The two residential blocks represent the equivalent of 50,000 sq m of single-family houses and support a number of trees equivalent to 20,000 sq m of forest. The result is high-density accommodation in a benign micro-climate, which absorbs carbon dioxide, filters dust particles, moderates temperature fluctuations and reduces noise pollution.
It is largely irrigated with grey water produced within the buildings and the green covering is thought to reduce energy consumption in the two buildings by 20%.
It has won international accolades both for its ecological innovation and its arresting visual impact, and in 2015 the Council on Tall Building and Urban Habitat declared it the most beautiful skyscraper in the world.
The towers support more than 750 trees and more than 15,000 shrubs and perennials. Planting consultant Laura Gatti advised on the selection of species and their requirements, based on three years of study. Tests took place in the wind galleries at the International Hurricane Research Centre of Florida, to see which cultivars could manage the exposure.
Around 600 trees were craned into position while the building was taking shape and the planting took place in three stages over three years.
According to Boeri, the diverse planting palette has had a radical impact on local biodiversity. He estimates that the towers initially drew in 1,600 specimens of bird and butterfly. Gatti has a five-year action plan to meet the changing needs of the planting.
Maintenance is carried out from inside the apartments eight times a year. Day-to-day watering is done by a drip-irrigation system controlled by sensors in the soil. The growing medium had to be light enough to minimise structural demands, but dense enough to support the long-term development of a range of trees, and it was specially developed for this project.
Given the height of the towers (one is 80m, the other 112m) there were serious safety concerns about anchoring such large specimens in their planting basins. A system of restraining cables and underground steel frames was developed, which satisfied the concerns of lawyers and horticulturists alike.