The Vertical Forest

This year in Milan city center is planned to complete construction of two unusual residential towers - Bosco Verticale («Vertical Forest”) is a building height of 80 and 112 meters, on which roofs and facades while planting a lot of vegetation, which will be able to hold 480 big and medium size trees, 250 small size trees, 11.000 groundcover plants and 5.000 shrubs (the equivalent of a hectare of forest).

Bosco Verticale
Boeri Studio (Stefano Boeri, Gianandrea Barreca, Giovanni La Varra)
Design fases: 2006 – 2008
Construction fases: 2008 – 2012
Structures: Arup Italia s.r.l.
Facilities design: Hilson Moran Italia s.p.a.
Detailed design: Tekne s.p.a.
Open Space Design: Land s.r.l.
Infrastructure design: Alpina s.p.a.
Contract administration (DL): MI.PR.AV. s.r.l.

Improvement of ecological situation of modern cities is a question of present interest. The Vertical Forest has at its heart a concept of architecture, which dematerializes urban areas and uses the changing shape and form of leaves for its facades, and thus which hands over to vegetation itself the task of absorbing the dust in the air, and of creating an adequate micro-climate in order to filter out the sunlight. This is a kind of biological architecture that refuses to adopt a strictly technological and mechanical approach to environmental sustainability.

Vertical Forest increases biodiversity. It helps to set up an urban ecosystem where different kinds of vegetation create a vertical environment which can also be colonized by birds and insects, and thus becomes both a magnet for and a symbol of the spontaneous recolonization of the city by vegetation and by animal life. The creation of a number of vertical forests in the city will be able to create a network of environmental corridors which will give life to the main parks in the city, bringing the green space of avenues and gardens and connecting various spaces of spontaneous vegetation growth.

Vertical Forest helps to build a micro-climate and to filter dust particles which are present in the urban environment. The diversity of the plants helps to create humidity, and absorb CO2 and dust, produces oxygen, and protects people and houses from the suns rays and from acoustic pollution. If we think of them in terms of urban densification, each tower of the Vertical Forest is equivalent to an area of urban sprawl of family houses and buildings of up to 50,000 square meters.

Trees are a key element in understanding architectural projects and garden systems. The height of buildings has not been determined by the presence of trees but by some kind of morphological and typological reasoning both in respect to the context and other architectonical emergencies to the boundary, and in respect to the functional program and the type of housing units proposed. In particular, the height of buildings was determined by the need to free up as much as possible land on the ground floor to be able to allocate it as park and public space. Compared to a previous project area, this solution in height leads to greater integration between the site and the future of the forest vertical park that characterizes the area of Porta Nuova.

In this case the choice of the types of trees was made to fit with their positioning on the facades and in terms of their height, and took two years to conclude alongside a group of botanists. The plants used in this project will be grown specifically for this purpose and will be pre-cultivated. Over this period these plants slowly got used to the conditions they will be placed in on the building. Protruding beyond the towers envelopes trees perfectly fit into the urban landscape, complementing the green panorama of Milan.

Certainly the trees and the land contained in the tanks, led to a greater load on structures. It is, however, preceded with the selection of a particular soil able to meet the nutritional needs of plants but at the same time was extremely light to minimize its impact on the dimensioning of structures. Regarding the theme of the wind, the plants do not increase the total wind load of the building. On this subject have been made special studies and tests in wind tunnel to test the reaction of plants and the forces that through the sod and root system are transmitted to the building structures.

Bearing structures of the building are realized in reinforced concrete in situ, as well as the floor plates that are also made with concrete and realized with a post tense system. The structure of the building is, in short, fairly traditional, this has allowed minimizing construction cost, while the innovative element is the solution of the facade.

The foundations of the Vertical Forest towers have not any unusual features compared to other buildings. The type of foundation, consisting of an armored concrete (respectively the thickness of 1.6 m for tower D and of 2.0 m for tower E), was chosen to make compatible the stresses transmitted from the buildings to the ground with the bearing capacity of the latter. Due to its weaknesses within an acceptable range the buildings will not be subject to deformation due to the land (an estimated maximum subsidence of about 60-70 mm). Providing a sufficiently rigid base to the building in order to control the deformability of the towers especially in dynamic conditions, due to conditions such as wind or seismic events.

The elevators and stairwells in general in both towers are located on one side of the building. Thus it was possible to organize in more efficiently, rational and free way the rest part of the floor surface. The solution of the façade with balconies and trees also covers, however, blind-sided where lifts flowing, so it can mask their presence outside, making them at a glance almost indistinguishable from the glazed areas.
The interior layouts have been designed till the final project. They were then elaborated and detailed by Antonio Citterio Patricia Viel and Partners study and by Coima Image study. In addition to housing and gardens in the “Vertical Forest” will open restaurants, fitness centers and parking lots. The design philosophy of the project requires that the terraces are extensions to the outside of the domestic space inside and at the same time they are green islands that penetrate inside. The whole project has been thought as the superposition in height of isolated houses with gardens, a sort of vertical sequence of garden villas. The relationship between outside and inside, between domestic space and space of the terrace, is the theme around which all other architectural and compositional choices go through. The apartments have denominations ranging from 57 to 255 square meters. Each of them has a terrace with trees; each apartment is involved in the particular design of the facades.

 Of course, the towers will be green not only outside but also technologically: there are provided solar and wind power stations, modern ventilation and lighting systems, and water recycling. In homes with greenery setout the irrigation and filtration system that will recycle waste water, making them suitable for watering plants. The project provides for the possibility of maintenance of existing plants as well as a complete replacement of all vegetation in buildings. Water supply and irrigation has been developed based on Milan climate studies and spacing of vegetation types on the buildings facades.

The building is complex not only with regard to the green theme, but in general is a project in which the plant and equipment are particularly important. With regard to the maintenance of plants, besides a drip centralized irrigation system controlled by a computer system, all the plants and soils will be regularly maintained in a inspection program and cutting plants and shrubs will be directly managed by the condominium and entrusted to specialized companies.

Changing its colors depending on the seasons Bosco Verticale complex could become not only iconic landmark of Milan but also interesting experience in creation a new type of urban landscape - the vertical one.

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Materials provided by Boeri Studio,photos Karola Merelli, Francesco De Felice