A very low carbon building concept

The construction world is not exempt from the dilemmas that challenge our time. We are always more and more eager for progress, comfort and technological innovations, but our planet is a finite environment, in which every resource is increasingly rare. However, we will always need infrastructure to live or work, which requires the sector to assign itself the following mission: to build with less impact, in construction and in use. Bouygues Construction is among those who want to take up this challenge. On the occasion of MIPIM 2023, the company unveiled its Archisobre “concept building”, whose history Fabrice Bonnifet, director of sustainable development & QSE at the Bouygues group, tells us about.

As an indication, in 2022, the building sector represented 18% of Co2 emissions in France. Faced with this observation, national legislation has gradually been strengthened to encourage the construction of more efficient and energy-efficient buildings: Since 2021, the RE 2020 environmental regulation has replaced its predecessor, RT 2012, by introducing new criteria for evaluating the environmental performance of buildings, in particular the carbon footprint, renewable energy production and adaptation to climate change. The goal is to reduce greenhouse gas emissions from the building sector by 40% by 2030, compared to 2019.

Although this regulation has been applied gradually, it now concerns all types of buildings, from individual housing to hotels to office buildings and sets maximum thresholds for CO2 emissions over the life cycle of buildings, which will be lowered every five years until 2050. In addition, France has set itself the objective of renovating 500,000 homes energetically per year, at least half of which are occupied by modest households. To do this, it has set up financial assistance mechanisms, but to achieve this objective, we still need to have solutions, so that our buildings are indeed environmentally friendly! Fabrice Bonnifet recalls: “The sector cannot continue like this, we are facing a technical and organizational challenge, to which we decided to respond with a project that breaks with the habits of the sector”.

For Bouygues, this breakthrough project is called Archisobre. Its objective: to divide by three the carbon impact of a tertiary building. It is the result of collaborative work between the teams of experts from Bouygues Construction, the design and environmental engineering agency Franck Boutté Consultants and three architecture agencies: NeM/Niney and Marca Architects, Coldefy and Martin Duplantier Architects. This concept is based on a bioclimatic architectural design using recycled, reused or biobased local materials. “For sourcing, Bouygues recently launched Cynéo” declares Fabrice Bonnifet “A center located in Yvelines entirely dedicated to the reconditioning of construction materials”.

While the use of reuse and reconditioned materials does represent a more ecological alternative to conventional materials, this is not enough to create the building of tomorrow. “It is an in-depth work, where the entire operation of the building has been redesigned” announces Fabrice Bonnifet. “High-performance low-tech solutions have been integrated to ensure the comfort of occupants while respecting the environment: natural ventilation, adiabatic cooling (which occurs without heat exchange with the outside) or use of the thermal inertia of the ground. The aim is to have a building in total harmony with its environment.”

Designed to be reversible throughout its life cycle, an Archisobre building is capable of transforming itself according to the needs of its occupants, and thus go from an office building to a building dedicated to housing, and vice versa. This principle makes it possible to limit demolitions and reconstructions, and therefore to reduce the environmental impact of the building. Archisobre's promise is to have a CO2 emissions level of 300 kg/m² over 50 years, three times less than the average for offices currently under construction.

With these arguments, one could imagine that this new concept would be all the rage, and that Bouygues' order book was filled to the brim. And yet that is not the case. According to Fabrice Bonnifet, “The market is very cautious [...] If Archisobre was originally a technical and architectural challenge, it is now a real marketing challenge. You have to convince and seek out the daring.”

Despite this apparent difficulty in finding the first customers, Fabrice Bonnifet was very enthusiastic. “The appetite for green buildings will eventually prevail, I think we will experience the same scenario that the automotive sector experienced with the electric car. If customers may be reticent when faced with innovative products, they will eventually adapt to them, helped by changes in thinking and legislation.”

Because in fact, French law will be tightened in the coming years to impose more stringent environmental standards on new and existing buildings. Current buildings that do not meet these standards will therefore quickly be caught up by regulations and will have to comply or be replaced by more efficient buildings.