
The following interview with Belgian eco-architect Vincent Callebaut, whose green buildings strive to reconcile nature and the urban world, was first published in French in December 2020 on the Fondation Bouygues Immobilier blog Demain la Ville. Translation by James Horrox.
What exactly is the “ideal city”?
The scheme of the ideal city is somewhat of a twentieth century idea. Our parents’ and grandparents’ generations dreamed of having a detached family house with a private garden outside the city — a city that had itself been imagined by modernists, notably Le Corbusier, as a living organism where each district represented an organ. This vision leads to the hyper-energy-intensive cities we knew at the end of the twentieth century. That is, cities designed in a mono-functional way: a business district in La Défense, a museumified city centre, bourgeois neighbourhoods, neighbourhoods for immigrants, residential housing in the suburbs…
This pattern made possible the explosion of automobile dependence and urban sprawl. A city that expends huge amounts of energy on heating, lighting and moving its citizens.
Where are we today? Climate change and the pandemic have renewed many debates surrounding urban models
For the past fifteen years, we’ve seen in Southeast Asia a phenomenon of de-densification of metropolises in favour of the countryside. Having built megacities of tens of millions of inhabitants like in Shanghai, they decided they could rebuild villages that are self-sufficient in energy and food, and hyper-connected to allow for continued teleworking. This is part of the famous ‘third industrial revolution’ theorised by Jeremy Rifkin — the addition of renewable energies and information and communication technologies (ICT).
Finally, this question of the ideal city is somewhat caught in a vice. As an architect, you have to respond to this contemporary schizophrenia: everyone wants to live as close to nature as possible while at the same time being hyper-connected. Today’s dilemma is how to join these two extremes together into a habitat. With the pandemic, this phenomenon has become more pronounced. This calls into question the pattern that we’ve been working with for years — the idea, repeated to us on loop by the media, that 75% of the world’s population will live in cities in 2050. If we manage to live happily in the countryside, there will surely be an inflection of this trajectory.
What is your approach?
The priority is to avoid horizontal urban sprawl, to safeguard the land and protect the soil from artificialisation. I’m one of a new generation of architects attempting to respond to these issues by condensing space. We work a lot on the serene densification of city centres, the revitalisation of rural and intermediate fabrics. The idea is to bring housing closer to the workplace and services so as to restore quality of life. It’s a bit like the concept of the fifteen-minute city.
Our proposal is to create vertical villages in the city. It’s a question of creating towers, not as in the last century, but with vertical or oblique interior streets that lead to different services — swimming pools, shared vegetable gardens, work spaces, party rooms or whatever it might be… We try not to put the core containing the stairwells, elevators and landings in the middle of the board, in the dark, but rather to outsource it, so from the elevator we see the city unfold. Rather like the escalators of the Centre Pompidou. We want to make people want to stroll vertically, so the most beautiful places in the building are open to all — including non-residents.

Is this part of your proposals for the Paris 2050 call for projects commissioned by the city of Paris?
Yes. We thought about how a city like Paris could densify itself, taking into account its magnificent heritage, and about how to implement a circular and virtuous economy in a European capital. We developed the concept of energy solidarity, which consists of a strong dialogue between contemporary architectures and heritage. Haussmannian buildings like those bordering three kilometres of the Rue de Rivoli can’t be insulated from the outside — they will remain thermal sieves — so we imagined contemporary grafts on the rooftops of Paris. These extensions produce the energy (electricity, heat) that historic buildings need. It’s a way of adapting a building so that it consumes less energy while preserving the land outside the city.
Whether in Cairo, Paris or Taipei, your projects have a strong, somewhat futuristic identity. Don’t they reproduce a kind of idealised city themselves?
We are part of a trend of “contextualist” architects. That is, when we develop a project, we imagine it for a specific site, a specific climate, a type of user and specific needs. You can’t transplant a project from one country to another, or from the countryside to the city, since each project is conceived according to the genius loci, the genius of the place. Each project is a different challenge, whose goal is to reinforce the identity that existed before — which was not the modernists’ approach to the ideal city. Our projects try to meet the needs of residents and the challenges of tomorrow’s city regarding density, green spaces, services and so on.
Aren’t they too focused on, for example, disruptive technologies?
In France we like to oppose contrasts: on the one hand, high tech, based on emerging technologies, and on the other, low tech, which relies on frugality and a reduction of needs. Whenever you embark on an architectural project, you start by analysing the local climate, such as the sun and the prevailing winds, to make sure you create buildings that are as compact as possible, and which reduce their needs to a minimum.
We are working on the inertia of buildings, with thick facades, exterior mantles, bio-based insulation in natural fibre that allows them to have a very low energy bill. In Cairo, the Gate Heliopolis project uses techniques that are 3000 years old, found in the temples of the pharaohs. The outside air (which sometimes reaches 40 degrees) is naturally sucked in by wind chimneys and passes under the foundations of the building, where it is cooled by the cooler ground before being pushed into the building. This is how a termite mound functions. We call it biomimicry.
After implementing this low-tech simplicity, we integrate technologies and renewable energies that have proven their worth. These technologies allow each building to produce its own energy, and in a decentralised fashion. It’s a complementary offering to nuclear power in France. In a way, we’re taking the best of high tech and the best of low tech.
Any final thoughts?
To conclude, I think there is no ideal city. It doesn’t exist. If the great dilemma of our times is how to create a habitat that is both connected and close to nature, I think that medium-sized cities can do well. By definition, they offer a quality of life on a human scale, which is simpler than in the city since they already have both services and nature.
