3 questions to Laurent Dandres, Construction Technical Controller and National Technical Reference for Biosourced Materials
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? Will the RE2020 help accelerate 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. 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.
Concretely, what are the steps to respect to integrate these materials in projects without taking risks and to respect the regulations? How far can we go?
As always when we intend to innovate in construction projects, the most important thing is to anticipate. Whether it is the will of the project manager to integrate biobased materials or the proposal of a project manager, it is essential to surround yourself with the right people to integrate them from the design stage: the architect of course, but also a technical controller. The use of biobased materials in construction projects can lead to technical and regulatory issues, especially if these projects are not part of a standard technique. The risk analysis performed by the inspector allows him to decide on the material and the installation technique. The favorable opinion is obtained after the expertise, on a case-by-case basis. Being well surrounded also means calling on ad hoc certified craftsmen. Integrating the various stakeholders from the start of the project is a guarantee of success.
On the rules to respect, there is first the risk analysis on fire safety, legitimately drastic and without room for maneuver. However, bio-sourced materials can have excellent performance in this respect.
Then, we must distinguish between common and non-common techniques. The first, which facilitate the insurability of the work are based on the Unified Technical Documents (DTU) or professional rules recognized by the Commission Prevention Products (C2P). It is also possible to resort to a Technical Assessment of Experimentation (ATEX), a technical evaluation procedure formulated by a group of experts on any product or innovative process whose development requires experimental use on one or more construction sites. With ATEX, the risk analysis is based on experimental techniques, the objective being for professionals to provide the necessary proof to validate a new construction method. Non-current techniques are still possible but require a very thorough risk analysis, always on a case-by-case basis, in order to ensure the prevention of hazards, which remains our core business.
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. Globally, if the client surrounds himself from the beginning with good professionals, and this is most often the case, a construction integrating biosourced materials is often very respectful of the environment and virtuous in terms of energy consumption for example. 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.
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Watch the interview with Laurent Dandres, biobased materials referent, on our Youtube channel.
Discover our article on straw bale insulation for Paris Habitat.
Watch the replay of our eWorkshop "Bio and geosourced materials: deciphering and impacts on your future real estate projects.
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