Bosco Verticale: Plants as Architectural Material
Gina Malfatti: Critical Terms in Modern Architecture Spring 2023
Let’s talk plants and architecture! When I think about how plants are used in buildings, I picture them as little embellishments. It is nice when buildings incorporate landscaping and offer greenspace, but it isn’t a requirement to feature greenery and vegetation in every building design. Maybe there is a rooftop garden on a high-rise, or decorative potted plants in designated areas.
Consider this though: what if plants were used as an actual architectural element, integral to the design and function of a building? Now imagine this scenario applied to a massive high-rise residential building. Ahhhh the dream! It sounds like an image of eco-friendly cities of the future, greenery and industry wrapped up in one. In Milan, however, Boeri Studios has made this a reality.
Bosco Verticale, or the Vertical Forest, comprises of a set of two residential towers in the Porta Nuova area of Milan, Italy. The taller of the two towers is 27 stories high and the shorter tower is 18 stories. Bosco Verticale was designed by Boeri Studio and completed in 2014. Bosco Verticale is located in an area previously filled with rail tracks and industrial buildings. The area is in the process of developing into urban park space, however, and Bosco Verticale acts as a beacon of natural elements in the neighborhood.
The buildings’ structure comprises of a typical curtain wall and reinforced concrete. The center of each tower contains the staircases, elevators, and utilities, which allows the exterior areas to function exclusively as residential space. Terraces decorate the exterior of the building-built out of cantilevered, reinforced concrete slabs on every floor and every elevation.
These cantilevered terraces act as outdoor spaces for residents, but they also serve the purpose of supporting and housing the 20,000+ plants that distinguish Bosco Verticale from other residential high-rises. The average tall-building type features glass as the primary cladding material; Bosco Verticale boasts an exterior clad in approximately 40% foliage, with the remaining predominantly bark-like clay panels. The architects designed the towers to appear ass giant trees in the middle of the urban landscape- hence the darker, bark-like panels used alongside the plants on the exterior. This design has been described as a “living green envelope” (Material Imagination in Architecture, Derne and Gaspari, 2016) and upon first look it is immediately evident why.
So, what does “vegetation” mean in terms of Bosco Verticale? The towers truly are a vertical forest- they include trees, large and small shrubs and bushes, ground-cover plants, and herbaceous perennials. Some of the trees even reach up to 6 meters tall. 90 different species of plants and over 20,000 individual specimens were installed in planters across the various terraces.
Ok, trees on a high rise, how can that be safe? Well, the team who constructed and designed the building spent years on research and testing to determine which plant species were suitable and could thrive in the extreme conditions that come along with such tall towers. Botanists and ethnologists were involved in the process, a great example of interdisciplinary architecture!
Wind resistance was a large concern, especially toward the top floors (no one wants trees toppling down 27 stories). To avoid this scenario, different tree species were tested in a wind tunnel to measure their wind resistance. A 1:100 scale model was used to test extreme conditions that plants might face. None of the trees bear large fruit or seeds (good news for anyone walking on the street below), and all species are amenable to pruning and require relatively simple maintenance. The selected plants are all parasite resistant as well.
Cultivating and planning the vegetation took years, but it wasn’t the only complex element of cladding a high-rise in plants. The structural support system for all the plants had to be carefully thought out and designed. Plants grow, so all the planters had to accommodate the plants they housed as younger, smaller specimens, as well as fully grown, larger ones. Weight constraints, root system requirements, and irrigation methods all had to be taken into consideration while designing terraces and planters.
So…. Why cover a building in plants? Well, the plants offer tons of benefits to residents, as well are the area around the building. All the vegetation helps absorb heat and creates less extreme high temperatures; this helps combat the urban heat island effect. The plants also help create humidity and their growth in the hotter months creates a barrier between the sun and residences. One of the healthiest impacts the plants have is on air quality. The abundance of growth acts as a giant air filter and improves the air quality for residents. All the vegetation has actually decreased the need for internal cooling systems in the building. Aside from environmental benefits, residents benefit from decreased noise pollution and gain all the psychological benefits of having an easily accessible greenspace in their homes.
Source: archdaily.com
The term “microclimate” is often used when discussing Bosco Verticale, and for good reason. Animals and insect populations benefit from the lush facades of the building. Biodiversity was a major consideration when designing the building. Over 20 species of birds can now be found amid the foliage, and there are at least 1,600 birds and butterflies that make Bosco Verticale their home. In cities with low levels of biodiversity, buildings like this can offer a unique way to bring species back into urban areas and help replenish endangered wildlife.
Bosco Verticale provides a whole new way of thinking about urban buildings. Boeri Studio, the team behind Bosco Verticale, plans to continue exploring the relationship between plants and architecture. Bosco Verticale acted as a kind of pilot project toward the end goal of creating ecology-centric buildings across the globe. They describe the project as a prototype building in their quest toward “a new format of architectural biodiversity which focuses not only on human beings but also on the relationship between humans and other living species.” (https://www.stefanoboeriarchitetti.net). Urban sprawl is becoming a major problem across the world and high-density buildings, like Bosco Verticale, can help combat that while still providing a high quality of life and access to nature.
Let’s talk maintenance. Bosco Verticale is like a giant, living organism with intricate systems that keep it going. The condo association of the building is responsible for all of the maintenance of the greenery. This means residents can take aa hands-off approach. Maintenance staff at Bosco Verticale are trained and knowledgeable about the care required for all the different plant species. They know all about what plants go in which containers and when plants need pruning or replacement. Understanding the lifecycle of each species is important when determining health and viability of existing plant specimens. When. Cleaning the façade and maintaining the plant life, maintenance staff actually uses mountaineering equipment to repel down the sides of the building. This (crazy) system allows them easy access to all the terraces without intruding on residents’ living spaces.
Above: A maintenance worker performing routine duties. Source: archdaily.com
Watering the plants is an essential requirement for a living façade! Irrigation system are like the little veins of the building. They are complex, since each species is unique in its water needs and tolerances. Plants also need different levels of water during different times of the year, so everything has been calculated and is rigidly maintained. Each façade of the building has its own system of irrigation. Factors like sun and wind exposure helped designers inform what fit best for each side of the building. Irrigation systems are attuned to the height of each terrace as well. Plants on the 3rd floor have different needs than plants on the 12th floor, for example.
Boeri Studios has stated that urban areas can act as their own solution to climate change, rather than exacerbating it. The incorporation of plants and natural environments into architectural developments is their way of pushing architecture toward a greener future.
Boeri Studios is not the only firm to take this approach- Parkroyal on Pickering in Singapore is another excellent example of incorporating plants and structures. Designed by WOHA, a Singapore-based firm, the building functions as a hotel. The building features “Massive curvaceous sky-gardens, draped with tropical plants and supporting swathes of frangipani and palm trees, are cantilevered at every fourth level between the blocks of guest rooms. Greenery flourishes throughout the entire complex, and the trees and gardens of the hotel appears to merge with those of the adjoining park as one continuous sweep of urban parkland.”
Like Boeri Studios, WOHA feels it is the duty of architectural firms to begin shifting in a more environmentally friendly direction. They view Parkroyal not only as a hotel, but a public architecture- the building benefits the whole city, not just guests of the hotel.
The idea of these botanical structures as public architecture is intriguing to me. The more of these buildings we have, the better the air quality, biodiversity, etc. are in any given city. They are a collective good in that manner. They also offer an aesthetic quality to city resident and visitors. They are green spaces that are accessible (at least visually) to anyone passing by (they also make for an interesting city skyline). However, when discussing what counts as ‘public architecture’ I feel cost is an important factor to take into consideration. Bosco Verticale is not quite affordable housing (it is in fact, pretty expensive). The same can be said for Parkroyal, not just anyone can afford to stay there as a hotel guest.
Until these kinds of buildings and spaces are available for a regular person to reside in and access, I would hesitate to refer to them as ‘public architecture’. Boeri Studios has made it clear that one of their long-term goals is to begin implementing some of these strategies in affordable housing developments as well, which is commendable and I look forward to following their progress toward that goal. Public and commercial buildings could offer a great way for all people to experience this type of architecture. Imagine working in an office building covered in plants, or going to school in what is essentially a forest!
The longevity and long-term success of these types of buildings is yet to be seen since so many have been constructed only within the last decade or so. Hopefully, the buildings will flourish and usher in a new era of architecture that connect humans, nature, and buildings. However, even if the buildings fail or do not perform as efficiently as expected, they provide valuable insight for architects about what works and doesn’t work when designing sustainable buildings in urban environments. The words “prototype” and “pioneer” have been used to describe these buildings and their architects, indicating they are the first wave and may not be flawless. I am incredibly interested to follow the progress of the buildings as they age and ass new techniques and technology develop.
As thrilled as I am about eco-friendly architecture, the preservationist in me is terrified of the implications these types of buildings will have on the field. Building materials are of particular interest to me, so when viewing a building I often think about methods of repair and maintenance for different types of materials. In this case, the materials aren’t static though. It I different that considering the replacement of a slate roof or the cleaning of unpolished marble. The plant themselves are a cladding material, if you take away the plant you produce a building visually and spiritually different than the original. I cannot imagine the sheer amount of knowledge a preservationist would need to have to recommend preservation strategies in the future for buildings like Bosco Verticale. Perhaps in the future we will study botanical materials as well as things like terracotta and metal.
The structure of Bosco Verticale is intrinsically tied to its living cladding materials, so the preservation of the building will need to address these materials explicitly. In 50 years or so a team of botanists and architects and preservationists and engineers etc. will be needed in order to preserve this revolutionary example of architecture. Interdisciplinary endeavors will become essential in the future as more of these projects are launched. The field of preservation changes alongside the field of architecture, so this vegetative-revolution in building materials will force preservationists to consider new approaches and acquire new sets of knowledge.
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