“People Have a Strong Demand for a New Proximity with Nature”: In Conversation with Stefano Boeri

Stefano Boeri describes his work as “Designing a home for trees”, and he is now working all over the globe, bringing his tree-based approach to trees from Mexico to Shenzhen. The architect believes in creating an ecosystem and not just a green façade. He also understands the importance of redefining our relationship to nature, particularly in cities.

Christele Harrouk, ArchDaily’s correspondent, had the opportunity to interview the architect at Eindhoven’s Trudo Tower, Stefano Boeri Architetti’s first social housing project. This was in collaboration with Francesca Cesa Bianchi (his partner at Stefano Boeri Architetti), Laura Gatti (botanist and plantation consultant) and Paolo Russo (project leader). The conversation focused on his relationship with nature and the environment, as well as his export perspective. It also covered the four ongoing vertical forests in West Europe.

ArchDaily (ChristeleHarrouk): Can you first tell us about how you approach forests? This is your signature move.

Stefano Boeri It is difficult to pinpoint the moment I began to have this obsession with green and how to build cities, forests and plants. I’ve always been very distracted by trees. Trees are a group of individuals we don’t know much about. We don’t know how they communicate or whether they can involve other animals and insects in their lives. This was something that I knew from my architectural background. However, 20 years ago in Milano, I began to realize this vision with a project to create an orbital suburban forest.

It was originally started in 2006, but the idea was born around 2003-2004. We planted 350,000 trees over three years in collaboration with Milano province. In those three years, nobody was even talking about forestation. In those years, I taught at GSD and was talking to my students a lot about Dubai as it was exploding. In fact, I was actually in Dubai when the idea of tall buildings with trees came to me. However, this was my post-explanation. It was also the paradoxical eruption of glass facades all over the desert that prompted the vision of something completely different.

Trudo Tower. Image © Stefano Boeri Architetti

I returned to Milano after that trip and was approached by the Porta Nuova team to design a mid-sized system in Isola. This is one of three components of the Porta Nuova project. After I had thought it over, I told the developers that I would love to design a highrise with trees. They told me I was crazy, that it was impossible for trees to be grown at such a high height, that it would cost a lot, and that the process of assembling apartments would be difficult. They gave me a list with very technical questions that I would need to answer.

This was a dream but it’s not impossible.

I began working immediately with a botanist and structural engineers. We filled that list with convincing answers, which allowed us to begin. This was the start of the vertical forest. The idea behind the vertical forest is to consider plants as part of buildings, rather than decorations.

Palazzo Verde . Image © Stefano Boeri Architetti

There were many technical problems right from the beginning. It started with the wind. Then it was irrigation. But we worked together to overcome each challenge step by step. In 2008, the financial crisis struck. At that point, the construction company responsible for the project was bankrupt. The project was halted by the collapse of the construction company. In 2012, we restarted the work. At that point, the first plants were moved from the Botanic Garden to the construction. However, it was completed in October 2015. We have nearly 10 years experience in understanding how trees respond to different environments.

Wonderwoods Tower. Image © Stefano Boeri Architetti

AD: There is a lot of skepticism around your approach. This is what you can tell us.

SB We began to study the structure and monitor its progress after the Bosco Verticale had been completed. After IIT Chicago, the first center to study the production and emission CO2, many other centers from around the globe participated. There was extreme skeptical around us. There were many people who claimed that within 2 years, 80 percent of the plants would be dead, the concrete will be completely destroyed by the roots, that there will be humidity problems, and that the trees will attract too much insects. People also talked about vertigo and how it was impossible for balconies to be built at heights of 50, 55 and 60 meters. Trees gave off a feeling of serenity and calm. Laura Gatti and I had chosen specific plants so that we didn’t experience any insect-related problems.

Wonderwoods Tower. Image © Stefano Boeri Architetti

It will be a jungle in 50 years. The building will be gradually overthrown by nature. It’s not so bad, is it?

AD: How has environmental quality been integrated into your work? Where did you get inspiration?

SB It was only later that I realized the need to make our city more green. Many people ask me where I got my initial inspiration. Inspiration is everywhere for me. Italo Calvino’s 1957 poem “Baron in The Trees”, Joseph Beuys, who planted 7000 oaks in Milano and transformed the space, and Friedensreich Hundertwasser, who arrived in Milano in 1972 and walked the streets declaring “trees our partners”.

AD: People are looking for your proposals from all over the world, including Mexico and Shenzhen. What is the secret to this success and its universality?

SB It’s not about Bosco Verticale. People are very keen to be in close contact with nature. It is also linked to the 18-months of Covid and psychologically with the serenity that plants can offer. Another thing that is increasing is the need for outdoor spaces. This is why we work so hard to get roofs installed in cities.

Palazzo Verde . Image © Stefano Boeri Architetti

The roofs will likely play the same role as courtyards did 50-60 years ago. They are a semi-private, semipublic space where tenants can meet.

It is amazing how we treated nature in the past centuries as something outside of us. Then suddenly, we realized that there was a microorganism within us. This has likely caused a collective shock. It was necessary to rethink our relationship with nature. It is also a response to this need for closerness with nature.

Palazzo Verde . Image © Stefano Boeri Architetti

AD: What is your work process? How do you approach each project? You said that you approach architecture from the context/tree rather than from architecture. Could you please tell us more?

SB Yes, we start with the tree. But that’s because, because we have this green façade where each species has its habitat (the forest), everything must be related to these species. This means that our design is guided by the selection of trees and plants. The selection of plants depends on the climate. I would call conditions and context the first step. With the assistance of botanists, the second step is the selection of greenery or trees. We start to think about colors and compositions at that moment.

Many critics claim that we hide the building by covering it in greenery. For me, plants are an integral part of the building, and not some decoration you can use for camouflage.

AD: What have you learned from Milano’s Bosco after 6 years? And what do you want to change in your next projects?

SB Each building is unique. While we must answer all the clients’ specific questions, we also have to make progress, learn from our mistakes, and come up with new ideas.

Trudo Tower. Image © Stefano Boeri Architetti

You will notice a difference in the soil level when you enter an apartment. There are times when the trunks start at lower levels and other times where the pods connect directly to the window. There are three to four ways you can be near plants. When we started in Milano, there were only two options. A variety of approaches leads to a richer relationship with plants. We have also developed a prefabrication system for Eindhoven’s project that can be used as a reference for architects and developers when designing green social housing buildings around the globe.

Wonderwoods Tower. Image © Stefano Boeri Architetti

AD: This is more than a green façade. It’s a way to create an entire ecosystem. What do you think is the most important result of trees on a facade? What are the benefits and consequences?

SB Many. One, in summer the building was able to lower the temperature and heat on its facade. The sun’s exposure to the building causes the shadow of the leaves to change dramatically. For example, in August, the air conditioners are not needed. You have many more benefits, such as pollution and micro-dust particles. There are over 20 species of birds that nest in the vertical forest, which is another advantage. It feels like you are part a larger ecosystem. Living there in close proximity to plants allows you to see your city through a green filter of foliage. It is so unique and changes your perspective.

In the past 20 years, we’ve learned a lot about how to create and design technical devices that emit less CO2. However, plants and photosynthesis are essential if we want CO2 to be absorbed.

AD: You just opened your first social housing project in Eindhoven, the Trudo vertical forests. How did this venture begin? What is the contribution of this project to Eindhoven’s city?

SB It began with Jack Hopkins’ meeting, a visionary who was present in Eindhoven during the start of the revitalization of this industrial hub, once home of the Philips industry. Phillips has been a part of Europe’s history for the past century. What we have around Eindhoven is simultaneously the concentration of the soul and total reclamation space and lifestyle. This is a remarkable example of regeneration. I was very attracted to the idea of creating a vertical forest for social housing here. It is a dynamic cultural and physical environment.

Trudo Tower. Image © Stefano Boeri Architetti

AD: What was the difference between creating affordable housing and a luxury residential building in Milano that was vertically oriented? How did you lower the cost?

SB This became my obsession. In a time when everyone was looking for it, how to make your ideas more efficient. It was basically the selection and use materials. This was a detailed and thoughtful study on prefabrication and how to reduce maintenance costs with methods such as the flying gardening.

Trudo Tower. Image © Stefano Boeri Architetti

AD: What are the specialities of the Antwerp vertical forest? What makes it unique and special? You have also started to build your first vertical forest Wonderwoods in Utrecht. How is the design evolving as the program changes and adapts?

SB There are four projects in this area of Europe. They are all located in a very close location, making it easy to travel from one place to the next. Our first social housing was built in Eindhoven. We have an L-shaped building in Antwerp that we used to be able to work on roofs and have green plants. We managed to grow a lot of trees on the roof. There were 80 trees. This project was originally intended to be affordable housing. However, the owner changed his mind and now the prices are quite fair. Another interesting aspect of Antwerp is the variable geometry. This is possible because the sliding glass windows allow for easy changes in the space’s dimensions. In Utrecht we are building the first mixed use program. In Brussels we are trying out a green facade for an existing office building.

We aren’t obsessed with a particular language when it comes to design. Everything changes when you consider nature as part of your work.