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The Vertical Forest and New Urban Comfort
by Stefano Boeri and Francisca Insulza

Pale, exhausted and overcome by the effort of running so far so fast, Daphne saw Peneus’s waters. “Father, help me!” she cried. “If rivers have divine power—this beauty that has made me so attractive, rid me of it, change me!” Even before her prayer was finished, her legs were slow and heavy; a fine layer of bark covered her soft breasts; her hair turned to leaves; her arms became tree branches; her feet, just now so swift, were rooted in the ground; her head was now the top of a tree. Only her shining beauty stayed. Apollo loved her still, and putting his hand on the trunk, he felt her heart still racing beneath the new bark. Throwing his arms around the branches as if they were limbs, he kissed the tree—and it shrank from his kisses, even though it was a tree.—Ovid, The Metamorphoses, 8 A.D.

“The history of the mechanization of environmental management is a history of extremists, otherwise most of it would have never happened.”—Reyner Banham, The Architecture of the Well-Tempered Environment, 1969

At a moment marked by decidedly self-conscious iconic design and edgy sensitivity about sustainability, our firm’s Bosco Verticale (Vertical Forest), the design for a high rise residential building totally encircled by an ecosystem of terraces that include trees up to nine meter high, seems, initially, as brazen as could be. How much greener could a building get? In fact, notwithstanding the idea’s local roots—the inspiration for the facade is the typically Milanese late19th-century, ivy-covered buildings and rooftop terraces of, say, Viale Majno or via Mercato—criticism, in the initial stages of the design presentation, flew wildly. Called naive, provocative, and downright silly, the project seemed to many not much more than a child’s drawing: perhaps beautiful but still dreamily utopian.

Yet many discussions, deliberations, and twenty-four months of serious R&D work later, a close look at the project allows us to flesh out the Bosco as a complex and feasible project that echoes the historical line drawn by Banham’s in his late ’60s The Architecture of the Well-Tempered Environment. For if, as Banham suggests, “in order to flourish, rather than merely survive,” humankind needs comfort, and this well-being, in large measure, “comes from the deployment of technical resources and social organizations, in order to control the immediate environment: to produce dryness in rainstorms, heat in winter, chill in summer, to enjoy acoustic and visual privacy,” then Bosco Verticale should in fact be read as a cultural and technological system that connects comfort and sustainability. The relation between the two is manifold and operates on different scales, from the unexpected creation of a forest in an urban hardscape, to the idea of stacked suburban homes, to that of vegetation as a comfort-creating “mechanical” device.

Certainly the desire to reconcile the culturally persistent duality of culture and nature is manifest. The desire to return to nature, to the forest, has been always evident in Western culture, but the return to a simple life in nature (think of Thoreau’s Walden) as a means of seeking the essence of being, now seems, considering present Western living standards, much less possible.

Current sustainability rhetoric is also a mode of seeking new ways of reconciling our existence with that of the natural world—now that we’ve consumed millions of acres of countryside, forced animals into confined areas, and left our mark on not only terra, but also water and air. And, with probable just cause, nowhere has this rhetoric been more insistently shouted out than within architecture. Conversely, amid the innumerable strategies for “building green”—from new facade systems and insulation to care in orientation and relations between solid and transparent, to reduction of water consumption, use of alternative energies, and low impact materials and construction¬—until recently little attention has been given to the integration of vegetation into buildings (through suspended gardens, green facades, and roof greening) as a tactic with wide-ranging possibilities of reducing the harms of construction.

The contemporary discourse on a new alliance between nature and urban life can be presented through three utopian ideals, each of which distinguishes itself by how it creates not only this connection, but also forms of domestic pleasure.

The first utopian model proposes a technocratic response through high efficiency mechanisms for capturing and channeling energy. It is linked to the widespread diffusion—within the domestic sphere, and encouraged by tax relief and ad hoc financing—of alternative energy systems (using heat pumps and active and passive solar, geo-thermal, wind power), of ways to convert rainwater into drinking water and to cleanse and reuse grey water, and of “smart” appliances. Although this model threatens a world of exaggerated control, its ultimate vision is compelling (if perhaps unrealistic): a complete energy revolution based on hydrogen technology, as described by Jeremy Rifkin, in which every building is a potential producer of electric energy that, connected through a “smart grid,” instigates horizontal production, consumption, and distribution of clean energy.

A second model proposes an artificial nature created through extensive incorporation of agriculture and vegetation in our cities, a model seen in such initiatives as the Vertical Farming project and Andrea Branzi’s Model of Weak Urbanization. Buildings that produce oxygen and mitigate heat accumulation, horizontal surfaces that create, at different levels, new planting and pasturing landscapes, policies that encourage proliferation of vegetation on both vertical and horizontal surfaces can be linked to new developments in food markets (farm shops, zero kilometer farming), while also leading to the “demineralization” of our urban environment. Urban agriculture integrated with domestic environments becomes possible.

A final model espouses reforestation and renaturalization of both peripheral and inner city areas. The notion of an urban wilderness with a great diversity of species—a non-anthropocentric vision of nature wildly reconquering the built environment, as in Gilles Clément’s concept of the Third Landscape —relies on policies that interrupt or suspend anthropomorphizing activities and create zones for nature to freely re-colonize the city. This process is already underway in areas of low density urbanization and in abandoned man-made precincts.

Born between the realization that inner city living is necessary for halting land consumption and that the suburban house and garden lifestyle holds lasting popular appeal, Bosco Verticale is a hybrid structure incorporating both. In its 18,000 square meter version (two towers of twenty-seven and twenty stories and a total 3,000 square meter footprint), each vertical forest constitutes in urban densification the equivalent of an area of detached houses of circa 50,000 square meters while over nine hundred plants occupy a forest-like 10,000 square meters. The Bosco feeds individual and collective attraction to nature. It subverts the principle of traditional enclosed green spaces (garden, parks), potentially integrating large plants into every inhabited space. It delightfully changes its skin according to the plants’ seasonal manifestations. The Bosco will also change over the long-term in synchrony with slow plant development, an on-going process that will no doubt incorporate unexpected plant forms, birds, and insects.

In addition to offering phenomenological pleasures, Bosco will perform as a forest, a unitary system. Through a careful selection and combination of over ninety species of plants and a technologically advanced irrigation system that, using and recycling groundwater, permits a constant monitoring and control of soil moisture, the project optimizes photosynthesis and generates a hypernatural microclimate that lowers summer temperatures and diminishes pollutants and carbon dioxide.

A residential tower edged by a forest also reproduces the comforts and pleasures linked with ideal homes. It mimics the close relationships between interior and exterior found in the single family suburban unit, bringing to mind the Los Angeles Case Study Houses, SITE’s 1981 drawings for a High Rise of Homes and Peter and Allison Smithson’s reflections on the domestic disposition and incorporation of modern appliances (see their Appliance House project).

In its programmatic resolution of the interior, the project proposes a concentration of the collective spaces of the home: the joining of sitting room, dining room, kitchen and terraces into a kind of internal patio that not only intersects inhabitants’ trajectories but also integrates the main technological, agricultural, and natural devices of the building. Hence, in a move away from the atomization of the domestic space in Tomas Maldonado’s concept of comfort, the apartments of the project propose a return to the space of socialization of premodern homes. The green system creates a natural filter that, producing shade in diaphanous summer and letting sun in during winter, protects inhabitations from unwanted light and acoustic pollution. The filter breaks traditional interior/exterior boundaries, making nature an intimate presence.

This presence, producing both pleasure and sustainability, at approximately 5% above normal construction costs, is further enhanced by the individuality of each garden, which, for technical reasons, is designed according to its own microclimatic conditions. The diversity of plants and their individual characteristics not only offer inhabitants an extraordinary perspective from within the apartment, but also participates in a rich beyond-the-building ecosystem including different species of birds and insects.

Bosco Verticale is a highly artificial machine d’habiter. And yet the technology, notwithstanding the technical demands of putting so many large trees in a single building, is centered on enhancing the natural predisposition of the vegetation. And it is in fact through this symbiotic effect between the trees and plants and the hardware of the building that the most comfort and pleasure is produced—a final assertion that brings us to a contemporary take on Banham’s thesis: the mechanisms that provide a “well-tempered environment” and thereby comfort and pleasure are to all intents and purposes, “natural,” not merely mechanical.

1. Bosco Verticale is a project by Boeri Studio (Stefano Boeri, Gianandrea Barreca, Giovanni La Varra), 2007.
2. Reyner Banham, The Architecture of the Well-Tempered Environment (Chicago: University of Chicago Press: 1984). Banham traces a history of the technical breakthroughs that, incorporated into architecture, have helped shape the environments we inhabit. Similar importance is given to mechanical conditioning within the modern house by Tomas Maldonado in his essay “L’idea di comfort” in Il futuro della modernità (Milano: Feltrinelli, 1987).
3. Reyner Banham, The Architecture of the Well-Tempered Environment (Chicago: University of Chicago Press: 1984, p. 18).
4. Evidence that this tendency is today changing can be seen in projects by Minsuk Cho, MVRDV, BIG, UCX Architects, Edouard François, and Ken Yeang, among others, that follow in the footsteps of Emilio Ambasz’s 1994 Fukuoka building or the less successful 1984 Quinto Palazzo Uffici della SNAM on the outskirts of Milan by Roberto Gabetti and Aimaro Isola.
5. Presented at the 11th Venice Architecture Biennale 2008, Sustainable dystopias is an on-going research project that explores the ideas surrounding the reconciliation between nature and urban space and directly plays with the contemporary rhetoric on sustainability. See .
6. Jeremy Rifkin, The Hydrogen Economy (New York: Tarcher, 2004). See also: Venice, Declaration. Revolutionizing Architecture to Address The Global Energy Crisis and Climate Change, September 2008, published on line at .
7. See .
8. Andrea Branzi, Weak and Diffuse Modernity: The World of Projects at the beginning of the 21st Century, (Milan: Skira, 2006).
9. Gilles Clément, Manifesto del Terzo paesaggio (Macerata, Italy: Quodlibet, 2005).
10. A meteorological and microclimatic study realized on the basis of the schematic design (2008) analyzed, floor by floor, the environmental conditions determined by the presence of green elements on the building, concluding that maintenance of optimal irrigation and thereby vegetation could produce a mitigation of heat, on the exterior of the building, of up to 2.5 degrees C in the summer months.
11. SITE (Sculpture In The Environment), described the Highrise of Homes project as a community geared to “accommodate people’s conflicting desires to enjoy the cultural advantages of an urban center, without sacrificing the private home identity and garden space associated with suburbia.” See: Envisioning Architecture: Drawings from The Museum of Modern Art, Matilda McQuaid, ed. (New York: The Museum of Modern Art, 2002), 220. A similar attitude is traced by Rem Koolhaas in Delirious New York (New York: Oxford University Press, 1978) in a 1909 drawing of the concept for a high rise: “A slender steel structure supports 84 horizontal planes, all the size of the original plot. Each of these artificial levels is treated as a virgin site, as if the others did not exist, to establish a strictly private realm around a single country house.”
12. The Smithson’s 1958 Appliance House assigns modern domestic equipment definitive locations in the home. Appliance containing cubicles hold all necessary connections thereby suppressing noise, vibration, and movement. The cubicles form the envelope of the house, determining its spatiality, while the interior is free to mutate according to the demands and wishes of its inhabitants.
13. Maldonado, op. cit.
14. An analysis of additional costs stemming from the presence of trees – slight structural reinforcement, plants and irrigation system – does not in fact have a high impact on the cost of construction. In ecological terms the fact that trees are local species, that water for irrigation is acquired from ground water – a condition that in Milan, a city with an excess of underground water, is deemed positive – and that the high presence of vegetation will aid in successive control of temperature seems to indicate no further environmental costs for the building.
15. An analysis of the microclimatic conditions at different heights and on different facades of the building, subsequently crossed with the characteristics of plants adapted to the Lombard environment, has been used to compose the position of different species of plants within the system of the green facade. As height increases, so does the number of plants with greater resistance to wind.