“For me, the material of the future is the one we reuse”

What are the major challenges facing the construction sector today?

Energy and environmental regulations for buildings are now forcing us to think not only about energy efficiency, but also about the carbon footprint and life cycle of building materials. This raises questions about the viability of certain materials, such as aluminium and concrete, which consume a lot of energy and have no environmental credentials. Then there’s glass, which is now a technical material that can limit the sun’s rays, but is complex to use and recycle. These materials are extremely damaging in terms of their carbon footprint, and for the moment there is no real solution to replace them.

Some are calling for a halt to all construction using these materials. It’s a bit radical, but it’s a radical approach that allows us to think seriously about how to improve things. In this respect, I think that in the next ten years or so, we’re going to see an evolution in the decarbonisation of concrete. We’re going to be able to use clay to replace cement, which still has a heavy carbon footprint.

Generally speaking, I think that all geosourced materials, i.e. those derived from our soils, will develop and combine with other natural materials such as wood. Today, there are still technical and insurance issues to be resolved in order to change the paradigm and enable the development of these materials.

What new materials are emerging and what opportunities do they represent?

There is a strong desire to return to old materials. You can see this in architecture schools. Young people want to reappropriate certain materials. A great deal of work is being done with stone to try and make it more accessible to the general public and reduce its costs, which remain the main barrier to its development. It’s a raw material that has enormous thermal qualities and requires very little in the way of secondary materials. Stone cuttings, for example, can be used to make plaster. Chopped or blown straw can also be used for insulation. These materials can be three to four times more effective than traditional wools. But they’re also natural materials that don’t tolerate humidity and require more care in their installation. However, for me, the material of the future is the one that can be reused, which means learning to work with what’s already there.

What is currently holding back the development of materials recycling?

The main limitation is the logistics involved in sourcing sites and materials for re-use. When a building is demolished, we should be able to find out whether there is any joinery, shutters, railings or floors to salvage. Consultations are now being launched by landlords, developers and public bodies to ensure this sourcing and to see, upstream of a worksite, what materials can be reused. There is a whole engineering process involved in finding out how to recover, sort and store these materials. This work can have a significant financial impact on the cost of a construction project and therefore considerably limit the development of reuse.

A number of groups of young architects and engineers have formed and are making this expertise in reuse their own. Start-ups are thinking about digital platforms for listing building sites and materials that can be reused. Some major groups, such as Bouygues, are currently buying up companies that reuse wood, recover polystyrene from demolition sites or are thinking about crushing concrete to turn it into a genuine reuse material.

Can these materials be made compatible with more sustainable construction methods?

Technology will enable us to make huge progress on these issues and avoid sending materials halfway around the world that we no longer want at home. We need technology to find new materials, but also to enable them to be recycled and reused. Many young engineers are working on this.

What consequences do you see for the use of these new materials and the reuse of old ones?

There will be a return to simplicity, to the vernacular. And a return to local production methods, which will enable us to reconnect with our regions and limit the carbon impact of transporting materials. In any case, there is a real awareness among all those involved in the construction industry. For me, the main challenge is to move away from the short-term view that drives up the price of materials. We have to stop saying that quality construction costs more. When you put a little more money into the materials used in a building, you pay back later in terms of its upkeep and, ultimately, its carbon footprint. In the future, however, we’re going to have to surround ourselves with specialists who know how to arbitrate between technology, regulations and new materials. There are some fantastic movements emerging today, such as those linked to frugality. Many architects and engineers have launched this movement around a manifesto. This type of initiative brings together extremely competent people who are driving things forward.