November 27, 2022: what will our cities and homes look like in the coming decades? How will we live with global warming?… These topics formed the basis of the US 50 debate and round table.earth university. This is the 17the edition was held on 25 and 26 November 2022 at the UNESCO headquarters in the heart of Paris with ten thousand participants and three hundred speakers from all fields of expertise.
Agnès Sinai, a lecturer at Sciences Po, jokingly sets the tone for the climate challenge: “Our civilization will make skiing possible in Saudi Arabia and impossible in the Alps”.
In the central region of urbanization, a speaker mentioned that following the current slope, the world’s three most populated metropolises by 2100 may be Lagos (Nigeria), Dar-es-Salam (Tanzania), and Kinshasa (Congo). ), each with a population of 80 million. Suffice it to say the scale of the issue.
As for the Western Hemisphere, Agnes Sinai points out that rather than over-metropolitanizing by forcing us to build tens of thousands of residential buildings in metropolises, it would be better to repair what exists and above all to revitalize small towns and villages. , including the historic centers are now empty and abandoned.
Christine Leconte, president of the National Council of the Order of Architects, agrees with the proposal, which applies to all construction: “Rather than building something new, it is important to restore and adapt what is already there! » The mayor of Versailles, François de Mazier, shares this view, especially since the building’s main greenhouse gas emissions occur during its construction. So don’t tear down the old one when you get this quality one!
This evidence should be extended to many other sectors, such as car construction: should civil servants in Brussels and Paris speed up the replacement of heat engine cars with electric cars? “carbon footprint” at best it will be positive after a hundred thousand kilometers?
At the same time, the architect notes that it is important to return the city to children: “In the last few decades, in new car-oriented settlements and in traditional villages with potholed and impassable pavements, children have gradually been pushed out of public spaces where it is impossible to move and play in complete safety.”.
In France, as in neighboring countries, there are many examples of beautiful rehabilitation and reconstruction of old neighborhoods (factories or residential buildings). But as the mayor of Saint-Germain-en-Laye regrets, the central administration does not go in this direction and encourages municipalities and inter-municipalities to build many new houses, which has the triple disadvantage of consuming a lot of energy – intensive materials, accelerating the artificialization of natural and agricultural land, and thereby endlessly expanding urban areas with the resulting travel problems (roads, bypasses, parking lots, etc.).
The project announced by President Macron to create regional express networks in ten provincial metropolises, such as the Ile-de-France RER, goes towards the concretization and artificialization of the surrounding natural spaces and fertile agricultural lands at all costs. metropolitans, to the detriment of the revival of peripheral France.
Proliferating skyscrapers is also urban and ecological nonsense. “I am not in favor of high-rise buildings at allFrançois de Mazieres emphasizes. The La Défense business district in the west of Paris is an ecological aberration! »
Contrary to what we might think at first glance, high-rise buildings, be it offices or apartments, are a waste of space and energy.
The corridors of the towers on the Esplanade de la Défense generate strong winds, which help cool the towers and require more energy to maintain the proper temperature inside them. Of course, the energy costs associated with elevator batteries and fire protection equipment are also added to this. The concentration of jobs also increases energy-intensive commuting.
High-rise residential buildings are not more efficient than the ground. A few years ago, the architect Remi Koltirine hinted at something like this “big set” The 1970s bordered on 7e In the Paris region, the density was lower than 15,000 people per km.2 of this district, one of the capital’s most posh areas, with its tree-lined avenues lined with blond limestone six-story Haussmann buildings.
If the construction of glass and steel skyscrapers is an ecological and rather simple human solution, the same applies to the mass use of these materials, such as cement. Cement production alone accounts for about 8% of all greenhouse gas emissions worldwide. However, this material is far from the virtues attributed to it. Architect Marc Held thus reminds us that it wears out and cannot be replaced unlike traditional materials such as earth, stone or wood. Reinforced concrete engineering structures need or should be rebuilt for the next century.
At the University of the Earth, Pierre-Andre de Chalendar, chairman of the board of directors of Saint-Gobain, is not afraid to demand a return to local materials for human, environmental and economic reasons. He is joined by Tokyo-based architect Kengo Kuma, who mentions his preference for wood, including large and imposing public buildings. It also emphasizes the importance of using natural ventilation as much as possible.
Since the beginning of time, there have been a thousand ways to maintain the right temperature inside a building, just waiting to be optimized and modernized. This is an urgent imperative because, as Christine Leconte points out, “According to the current curve, there will be 4 times more air conditioning in 2050, and air conditioning with concrete will be one of the main factors in increasing greenhouse gas emissions! »
By returning to local materials, respecting the environment as well as the identity of the cities, and promoting urban greening by providing open spaces where tall trees can flourish, these are the goals set by the mayor. François de Mazieres: “Blonde Versailles and rosy Toulouse both owe their extraordinary beauty to the material from which they are made, here limestone from the basin of Paris, there brick from the Garonne. »