Bio-based construction
back to the future...

Focusing on bio

The world is changing fast, and so is language. New words are being coined, hybrid creatures that give substance to new realities. Immunocompromised, climate realist, Nutriscore... Bio-based was added to this bestiary in 2016. This term describes materials derived from renewable organic matter (biomass) of plant or animal origin, as opposed to geo-based materials, which are of mineral origin, or petro-based materials, which are of fossil origin, which bio-based and low-carbon geo-based materials aim to replace.

According to a report on the subject published by ADEME in February 2025, bio-based products have gained respectability over the past 10 years and now account for 4.4% of the overall market in France in terms of volume and a respectable 10.8% in terms of turnover. « We’re no longer just a blip on the radar and the signal is no longer weak, » Loïc proclaims. To the detriment of conventional products of fossil origin or those with energy-intensive manufacturing processes that emit greenhouse gases, this breakthrough is very clear in construction, cosmetics, hygiene, paints, detergents, inks and, to a certain extent, textiles. In 2015, at COP 21, 196 countries ratified the Paris Agreement. The development of a genuine bio-based industry is one of its major legacies.

What are the benefits of using bio-based materials as an alternative to what has been working very well for decades? “Of course, reducing our carbon footprint is an obvious priority in the context of the hunt for greenhouse gases,” Erwin points out. Bio-based materials, with their carbon sequestration properties, have long earned their stripes in terms of environmental respectability. “But there are also major advantages in terms of job creation potential, local economic resilience and eco-circularity, and preserving user health.” Loïc adds: « France is 90% forest and agricultural land. It would be wrong not to take a serious look at this potential. » Bio-based materials (wood, straw, hemp, flax, rice husks, rapeseed, cork, etc.), low-carbon geo-based materials, i.e. those whose manufacturing process emits relatively little greenhouse gases (we are talking here about clays, raw earth, etc.), all of which sound a little medieval, yet can be exploited, either directly or as processed residues, by integrating them in a modern way across multiple industry sectors.

Construction, a heavyweight in bio-based materials

At the turn of the 20th century, the 330-metre Eiffel Tower stood as the proud emblem of the industrial age — coal, steel, oil. Let us hope that in this first quarter of the 21st century, bio-based construction will also become the standard-bearer of an eco-economic revolution, bringing us closer to the desired goal of carbon neutrality by 2050.

Proof of the sector's vitality, in 2017 around fifteen manufacturers involved in bio-based construction in France created the Association des Industriels de la Construction Biosourcée (AICB). Things are really taking off in the bio-based ready-made sector!

Here are a few figures from the latest AICB report on this burgeoning sector: 19 production units in France, 4,000 direct and indirect jobs, €150 million in investment since 2020, 28 million m² used per year. Only a meagre 2% of the annual bioresource pool is exploited, yet existing production capacity could cover an area of 60 million m². This potential cannot be ignored at a time when flagging economic engines are looking for ways to accelerate growth.

Structural and insulating roles

In major structural works, two low-carbon candidates take the lion's share: timber, among bio-based materials (maximum 7 storeys), and its geo-based cousin, earth (between 3 and 5 storeys in our regions), whether raw, fired, compressed (or not) and mixed or not mixed with straw. Straw itself, of which only 10% of residues are currently used in construction, is just beginning to emerge as a viable structural material

In finishing and insulation, materials such as cork, straw, flax, rapeseed and rice husks are successfully used for their thermal and acoustic properties and their reduced emissions of Volatile Organic Compounds (VOCs) and Persistent Organic Pollutants (POPs). They contribute to healthier indoor air and regulate humidity naturally — preventing mould and damp², while improving the lifespan of the building.

“The costs of bio-based materials vary from one solution to another, and to compare them with conventional solutions, you have to analyse not only the purchase price, but also the implementation and operating costs over the lifetime of the building,” Loïc points out. “Almost without exception, eco-sourced materials require specific expertise to implement, which really enhances the value of the building trades,” he summarises. Decision-makers will have to weigh up the eternal budgetary dilemma between capital expenditure and operating expenditure in order to choose the best balance between CAPEX and OPEX.

Is there a downside to bio-based materials?

At this stage, the story is appealing, even compelling. Let us therefore dare to be a little eco-realistic without sinking into grumpy fatalism! Bio-based materials also have flaws, which can certainly be corrected, but which need honest scrutiny.

The minimal carbon footprint of bio-based materials is reassuring. But rigorous eco-responsibility requires a complete analysis of the material's life cycle. « If, in order to produce rice husk-based insulation, industry players deforest Asia, sow GMO rice, deplete the soil, eutrophicate and pollute waterways, and transport the material over long distances with high CO₂ emissions, the total negative environmental footprint will not justify the few square metres of virtuous insulation, » explains Erwin.

A few years ago, it was sufficient in terms of regulations for buildings to comply with RT2012 (RT for Thermal Regulations). The aim at that time was simply to cap a building's energy consumption. RE2020 (RE for Environmental Regulations) replaced this standard in 2020. This more ambitious regulation defines new construction methods for new buildings based on three criteria: energy efficiency, carbon footprint reduction and indoor comfort (temperature, humidity, air quality).

“Renovation is still exempt from restrictive regulations, even though it offers real potential for energy savings and carbon emission reductions. We can lament this for now, but we can also work on it by seeing it as a real opportunity for progress,” says Loïc.

An evolving legislative and regulatory framework

This RE2020 initiative is part of the Energy Transition and Green Growth Act (LTECV), passed in 2015, which sets out the main objectives of the French energy model in line with the desire to establish a European Energy Union. The LTECV incorporates the concepts of green growth, job creation, reduction of energy bills, circular economy and waste recycling... the equivalent of a full English…

The legislator is moving quickly and setting desirable objectives. The field is adapting, moving according to its means, oscillating between carrots and sticks, incentives and constraints. The framework is in place, and for many, so is the will. All that remains is to face reality.

“In our region, the EnvirobatBDM association has created the BDM standard for Sustainable Mediterranean Buildings," comments Loïc. Based on a multi-criteria grid that encourages better building by rethinking water and energy consumption, comfort through bioclimatic design, air quality and occupant health, the BDM label (bronze, silver or gold) has recognised 17 major projects since 2016.

“In the building industry, the discourse around bio-based materials has permeated many manufacturers, which was not the case ten years ago when a form of condescension prevailed,” says Erwin. Between CSR policy, recruitment arguments and the temptation of greenwashing, companies at regional, national and European level now seem to have moved beyond awareness to genuine confidence. The bio-based dynamic can be seen in communications, in figures and, most recently, “in companies' requests for universities to train people in bio-based engineering,” concludes Erwin.

A hot topic, the position of insurance companies...

There remains the delicate issue of insurance, particularly with regard to the behaviour of bio-based materials in fire. Some materials are naturally slow to spread fire. Others require specific treatment to slow down their combustion. Opinions are still divided, and characterising the behaviour of a material in fire is not so simple. Fire experts analyse it in three dimensions: reaction to fire, resistance to fire and finally fire transmission. Assessments are underway, guides have been partially established... and, understandably, insurance companies want to avoid getting burnt.

They’re also assessing the structural durability of these buildings over time³. Not all bio-based buildings receive the blessing of the ten-year warranty advocates, and this topic is broad enough to merit another article. There is a green list published by the Commission Prévention Produit, a body that brings together insurance and construction professionals and produces ATec (technical opinions) and DTA (technical application documents). In short, among bio-based materials, as elsewhere, there are those that have already proven themselves in terms of insurability, and others that are in the process of doing so.

Bio-based, popular on paper but still a long way to go

In the current climate and ecological context, bio-based materials appear to be legitimate, but not yet entirely necessary in terms of their economic appeal. However, they are no longer invisible and are benefiting from the establishment of dedicated institutions and investments that are helping to create a credible industry. The risk-reward ratio is leaning towards the positive side, which is enough to inspire new talent and attract budding entrepreneurs.

Bio-based materials have evolved, the larva has metamorphosed and has just emerged from its chrysalis. The sector certainly has more (pleasant) surprises in store... It's the butterfly effect. In a good way!

1. Source: report by the Association of Bio-based Construction Manufacturers, 26 March 2025

2. It is the concept of the dew point of water vapour that creates water droplets on interior surfaces.

3. The oldest French straw building is over 100 years old! https://cncp-feuillette.fr/la-maison-feuillette/

Some players in the bio-based and geo-based industries on the French Riviera:

www.terres-fibres-azur.fr (Bar sur Loup)

www.scic-tetris.org (Gréolières)

www.filiater.fr (Nice)

www.charpenterie-dautrefois.com (Roquebrune sur Argens)

Events to follow in the Var and Alpes Maritimes regions:

TERRE construction meetings in Cuers (10 October)

Eco Habitat 2025 trade fair in Vence (7–8 November)

Eco-housing trade fair in Le Cannet des Maures (28–29 November)

Associations:

www.batiment-biosource.fr, the website of the Association of Bio-based Construction Industries

www.envirobatbdm.eu, collective intelligence for better building

www.permabita.fr, the link between producers and users