Construction and renovation: how to take advantage of biobased materials in complete safety!

Hello Laurent. You are an expert in biosourced materials. There has been talk of an explosion in the use of these materials in recent years. What does biobased material represent in the construction and renovation sector in France and in Europe? Has the RE2020 help accelerated the adoption of these materials? What are the prospects?

The generic term "biosourced" is used in everyday language to refer to two types of materials: biosourced materials, which are partially or totally derived from biomass (wood, hemp, rice husk, straw, flax, etc.) and geosourced materials, which are of mineral origin (raw earth or dry stone). Basically, we are rediscovering and perfecting ancestral techniques, not to say prehistoric ones... To come back to your question, I saw the market being born about fifteen years ago, at the time we had a project from time to time, in a sporadic way. For the last 3 or 4 years there has been a clear acceleration with now solicitations every week. Generally speaking, we see the different sectors (hemp, straw, raw earth...) getting organized and working on new construction techniques. The knowledge of these techniques is democratized, it is an interesting moment for a market that is becoming professionalized. At the European level, countries like Germany, Austria and Switzerland are quite advanced, with strong sectors and their own techniques that correspond to local materials. This is an important point in the almost philosophical logic of biobased materials: generally speaking, we prefer materials that can be found nearby, which avoids costly transportation in financial and environmental terms.  The corollary is that construction techniques that are valid in Austria are not necessarily valid in France and vice versa, so there is no European standard today. 

Coming back to France, I think that the market will continue to develop, not only does it correspond to a strong aspiration of the citizens - that we find in public and private tenders - but the characteristics and performances of these materials are excellent. They are generally locally produced, minimally transformed, and have a low environmental footprint. Applications for new construction and renovation are numerous: structure, insulation, rendering, roofing, cladding, etc.

Furthermore, the 2020 Environmental Regulations (ER 2020) encourage the use of biosourced and geosourced materials in construction projects. These materials are perfectly suited to the 3 challenges of the ER 2020: reducing the impact of new buildings on the climate, controlling energy consumption and improving thermal comfort. Straw, for example, has the advantage of being one of the most perspiring materials: concretely, it absorbs and evacuates humidity, thus offering a very good air quality, we speak of hygroscopy. Finally, it should be noted that the resources are important. For example, 10% of the wheat straw produced annually would be enough to insulate all the new housing built each year in France according to the association Collect'IF Paille.

Finally, the RE 2020 will indeed promote the use of biosourced and geosourced materials, because the future environmental regulation for new construction will take into account, in addition to energy efficiency and production of renewable energy, greenhouse gas emissions (GHG) generated throughout the life cycle of the building, from resource extraction to deconstruction, through the phases of manufacturing, construction, use and maintenance. Biobased and geobased materials generally have a low carbon footprint and, for some, insulating properties. They are therefore particularly well suited to meet the challenges of RE 2020.

What is your role at Apave in concrete terms? Public and private project managers?

As a technical inspector, I work with my colleagues to prevent technical hazards. We are present from the very beginning of the project, providing expertise and analyzing the risks in terms of fire safety and solidity, and we decide on the best solutions in terms of durability and safety. For fire safety, there are the regulatory texts that we mentioned; for solidity, we base our analyses on the standards and texts. On particularly innovative projects, feedback feeds the reflection, we advance step by step, we also encourage the realization of tests to find the right solution. We can also support the project with the insurance companies and in this sense have a role of facilitator of the change. Surrounding yourself with the right professionals from the outset is a guarantee of success for any building project using bio-sourced materials. Anticipation is essential! I can give you a particularly innovative example, for the Jacques Chirac leisure center project in Rosny-sous-Bois in Seine-Saint-Denis. It is an avant-garde project and a precursor of the sustainable construction movement with straw bearing walls. To validate this choice, we followed tests with pre-stressing of the straw using straps. The fire resistance of the straw wall was tested in the laboratory, as required by law. The results were convincing. We must not be afraid to ask the right questions and to go to the end of each step. This is the right way to do good things.

At Apave, we have a strong track record and word of mouth is working. At the beginning, we had a lot of projects from local authorities, but today this is becoming more democratic and we also have more and more projects from the private sector.