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The return of eco-materials

In October 2018, the IPCC report recommended replacing concrete, steel and aluminium with eco-materials in order to give us one more chance to remain under the 2 °C global warming limit—or if possible, the 1.5 °C limit—and comply with the Paris Climate Agreement.

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“Eco-material”, a common term since the 1990s, entered the French dictionary in 2019, where it is defined as a “construction material whose use respects the environment”. It includes stone and raw earth (geosourced, mineral-based materials), as well as wood, straw, hemp and reeds (biosourced materials that come from plants or animals). For the construction industry, which is responsible for one third of domestic greenhouse gas emissions, according to a June 2019 study by ADEME and Carbone 4, these natural materials are a major source of interest. Extracting, harvesting or sawing these materials requires relatively little energy, and they can be recycled, reused and processed with a lower environmental impact than other materials. 

Their lifespan is counted in centuries: even the straw used in Feuillette House, which was built in Montargis, Loiret in 1920, still maintains its original properties. And to top it all off, some geosourced or biosourced materials have excellent thermal properties in terms of insulation and heat capacity. The 2020 Environmental Regulation (RE 2020), which enters into effect in summer 2021, “should make the use of wood and biosourced materials”, which are capable of storing carbon, “almost systematic by 2030, including for individual homes and small apartment buildings”, according to the press pack issued by the Ministry for the Ecological Transition. This process should reduce buildings’ carbon footprints throughout their lifecycles, from construction to demolition, while also ensuring comfort during winter and intense heat. 

“At the same time, a government label will allow public or private contracting authorities to anticipate the future requirements of RE 2020, set an example, and serve as a prelude to future buildings farther down the line.” These measures will trigger a radical shift in building types and construction methods, “which will require site workers and tradesmen to alter their practices and undergo training. This is particularly true when it comes to using wood and biosourced materials, which will substantially change how construction sites are designed, supplied and managed.”

However, a quarter of the country’s 2050 housing stock has not yet been built, according to projections released by the Ministry for the Ecological Transition (to address concerns raised by the decrease in household size and demographic growth), and multiple long-term economic issues have arisen. First, the need to supply eco-builders with eco-materials. There will be no shortage of earth, straw, hemp and reeds, according to their respective industries. However, the country’s 500 stone quarries cannot be endlessly tapped, and there are serious threats to forests, according to the April 2020 report from the Court of Auditors (Developing the Forest-Timber Industry, Its Economic and Environmental Performance).

These threats include climate disruption, an excess number of large game animals (which impede forest replenishment), and unfavourable opinions toward hunting and logging. This restructuring of the forest-timber industry, which is running a deficit due to log exports (particularly to China) and imports of processed products such as CLT, is vital. 

it's tweeted!
Emmanuel Macron
The President of the French Republic, on Twitter in April 2018.
“France has one of the largest forests in Europe, but imports wood for construction—that means there’s a problem! We have to reorganise the industry. It will create many more jobs.”

Only ambitious public action will enable this reorganisation, notes the Court of Auditors. These recommendations—a new environmental regulation, substantial financial assistance—have been followed. On 22 December, Julien Denormandie, the Minister of Agriculture, announced a 200-million-euro relief package to replant 50 million trees in the country’s forests. On 16 December 2020, BPI France launched a 70-million-euro Wood and Eco-Materials Fund to prop up the industry. The ball is in their court. 

A few companies and projects that are earning buzz

The foundations for tomorrow’s buildings have already been laid. Often compared to the homes of the three little pigs, a number of straw, wood and brick buildings from major construction companies and fledgling developers, like REI Habitat and Woodeum, are making headlines. Having earned E+C- labels (for positive-energy and carbon-reduction buildings), these innovative structures, inspired by the past, helped push through the 2020 Environmental Regulation bill, even before they were subject to its rules. They have “set an example and serve as a prelude to future buildings farther down the line”, to borrow the words of Emmanuelle Wargon, Minister Delegate for Housing to the Ministry for the Ecological Transition—and for good reason. 

Materials traceability

Using eco-materials and working as much as possible with whatever is on hand or underfoot represents a revival of common-sense practices that were already recommended two centuries ago by Léon de Perthuis, in his Treatise on Rural Architecture: “If the locality did not present (...) any construction-worthy stones, [the owner] would be forced to employ in his constructions either wood, fired brick, mud brick or rammed clay, according to the nature of the available lands. And so, after surveying the local resources, he would assign, in proportion to the elevation required for the walls of each building, the variety of fabricated materials most economical and at the same time most suitable for the degree of solidity its purposed demanded.” 

The public delights in reading about the origin of the ashlar used in the Le Metropolitan project (a group of 283 homes under development by Verrecchia Construction in Rosny-sous-Bois, Seine-Saint-Denis): the Saint-Maximin quarry in the Île-de-France region. 
They enjoy learning that in order to complete a project in Confluence, Lyon (a 1,000 m2, three-story building designed for Ogic by architecture firms Clément Vergély and Diener & Diener, which was made with rammed clay—a traditional technique from the Rhône-Alpes region), Nicolas Meunier’s team used earth from an excavation site less than 20 km away. 

La Maison des Plantes, Bâle.

They are pleased to discover that the earth used to build La Maison des Plantes de Ricola in Basel, Switzerland—the largest rammed-earth building in Europe (at 110 m long, 29 m wide and 11 m high, it was designed by Herzog and de Meuron and built by Lehm Ton Erde de Martin Rauch)—partially comes from the site itself, and from a quarry 10 km away. And they take comfort in knowing that if these buildings were ever destroyed, they would return to the earth they came from. As part of the same circular economy process, excavated material from the future Grand Paris Express site will be used to build an entire raw-earth neighbourhood by 2030 in Ivy, Val-de-Marne, on the site of the former Paris waterworks plant. The material will be converted into bricks at a factory created two years ago in Sevran, and will then be used to build earthen, stilt homes over a tract of water.

The chief architect of this project, dubbed Manufacture-sur-Seine, is none other than Wang Shu, winner of the Pritzker Prize in 2012.

The builders have pledged to use traceable materials, as in the restaurant industry. “For each stud, each floorboard, we can tell you who the manufacturer is, and which massif it comes from”, promised Paul Jarquin, Chairman and CEO of REI Habitat, during his presentation on L’Hester, a property-development project that delivered a twenty-unit, “locally sourced” apartment building in early 2020. The builders also pledged to indicate which forests the wood (primarily spruce) came from: the Grand-Ouest region, Massif Central, Jura or the Savoie Massif. Working with local materials whenever possible, and with local partners, is also the goal of Bouygues Bâtiment France Europe.

The company has contracted several regional companies to build the headquarters of Podeliha, a social housing provider in Angers. These include Piveteau Bois, a company based in Vendée that specialises in making CLT panels, and Caillaud Bois, a family-owned company based in Chemillé-en-Anjou, which will lay the panels and manufacture and install the framework, studs and beams. 

Natural architecture and well-being

The return to using local materials and local partners has created a boom in the natural architecture prized by Kengo Kuma—a happy marriage between architecture and location, where buildings are imbued with a “natural” feeling. 
Inspired by Japanese temples, the Saint-Mandé apartment block, whose structure and façade are made entirely of wood, adds a touch of calm and lightness to the ‘70s-era concrete complex in which it was built, on boulevard Saint-Mandé, in the twelfth arrondissement of Paris. Its fourteen additional apartment units blend in seamlessly with the trees in the courtyard garden. It was delivered by Bouygues Bâtiment Ile-de-France in September 2020.

In the countryside, Jean-François Daures’ green school complex in Montpezat-sous-Bauzon, near Aubenas, which was delivered in 2014 and won the Sustainable Construction Grand Prize at the Green Solution Awards in 2019, is in perfect harmony with the surrounding scenery. Vegetation is everywhere: in the Douglas-fir superstructures, sourced from the Cévennes region, as well as the roofing, the cladding and the scenery. Even the road that runs by the school has been decorated with greenery. The idea, according to the architect, was to “pull the prairie green over the school complex, covering it in a plant canopy”, and to showcase local biodiversity. The teachers have all noticed a marked improvement in their student’s well-being, as well as an increase in academic performance. In Aerem’s straw and wood factory in southern France, delivered in 2018 by the Toulouse-based firm Seuil Architecture, the workers say it’s easy to forget about the winter and poor weather, which are more noticeable in concrete buildings.

Angers Hospital
In an article in La Dépêche on 2 May 2019
. “Multiple studies have demonstrated the beneficial effects of a wood environment on the health and well-being of its occupants. However, few hospitals use wood due to its porous surface, which is seen as unsuitable in environments vulnerable to microbial infections. This may require cleaning or lead to cross-contamination, hospital-acquired infections, etc.”

However, in Canada, studies show that cancer patients recover more quickly in such an environment.

Feats of architecture and urban planning 

Using eco-materials doesn’t rule out bold architectural styles. Wood, which is five times lighter than concrete, allows for construction in the French capital, which is already highly dense, as well as in underground car parks—as was the case with the Saint Mandé apartment complex. The material is also being used by Woodeum to build a three-building residence hall for students and young athletes over the Paris ring road at Porte Brancion, and was also used to add five floors to a supermarket at Place de la Nation.

 But what the press is celebrating most of all is “the tallest wooden building ever constructed”. Mjøstårnet, in Brumunddal, Norway, currently holds the record with 85.4 metres over 18 storeys. In France, the Hyperion residential tower block (57 metres tall, 17 storeys), which is under construction in Euratlantique, Bordeaux, will be completed in May 2021. Developed by Eiffage Immobilier, the building is set to dethrone the current tallest wooden tower (38 metres) at the “Sensations” building complex in Port du Rhin, Strasbourg, which was delivered by Bouygues Bâtiment Nord-Est in 2019. French architecture firm Rescubika Creations has proposed building a 160-storey wooden skyscraper, dubbed Mandragore, on Roosevelt Island in east Manhattan, but for now it remains just an aspiration.

Industry structuring

The growing appeal of new techniques since the end of the 19th century—including concrete and steel—as well as the wartime loss of manpower and expertise passed down from prior generations, have weakened the wood, straw and stone industries since the 1960s. However, these industries are still in the picture, and the new environmental regulation (RE 2020), which is designed to reduce buildings’ carbon footprints by encouraging the use of biosourced materials, should pick up their burgeoning momentum once it is implemented in summer 2021. 

Main industries 

Straw is an abundant resource in France, with 10% of its annual production capable of insulating every building, according to the French Straw Construction Network (RFCP), and the straw industry itself is the most dynamic in Europe, with 500 annual builds and a growing number of buildings insulated. The hemp industry, whose top European producer is France, is in a similar position. Nothing on the plant is wasted: the fibre (husk) is used as insulation, and the shives (the woody centre of the stalk) are used to make coatings and vegetal concrete for renovations and new builds.

Stone, for its part, still boasts 715 specialised companies and 4,000 direct jobs, with revenues of 515 million euros, according to figures from the natural stone industry. Lastly, raw earth, which is promoted by the CRAterre  association, will be the subject of a “national project” currently under development by the Ministry for the Ecological Transition. The forest-timber industry carries the most weight. According to the April 2020 report from the Court of Auditors (Developing the Forest-Timber Industry, Its Economic and Environmental Performance), the sector accounts for 440,000 jobs (compared to 1,200,000 in Germany) and 60 billion euros: 20 billion upstream (logging) and 40 billion downstream (the wood processing industry, including real estate developers, sawmills, carpenters, joiners, energy engineers, papermakers, etc.) 

Paradoxes of the forest-timber industry

However, the industry in France is characterised by a series of paradoxes that are impeding its development, according to the report from the Court of Auditors. 
France has been unaffected by deforestation: its forests have doubled in size over two centuries, due to the spontaneous afforestation of abandoned agricultural land. They cover one third of the country, and constitute one of the largest forest areas in the European Union, after Sweden, Finland and Spain. 

However, only half of its annual growth is harvested, and it is poorly integrated between the upstream and downstream ends of the industry, between supply and demand: it exports less rough timber than it imports processed products, leading to a substantial, seven-million-euro trade deficit, which widened by 4% between 2018 and 2019, according to an August 2019 report by Agreste Infos Rapides (Wood and Wood By-Products). With a forest area 45% smaller than that of France, Germany’s lumber production is almost three times higher (23 billion m3 vs France’s 8 billion m3); Austria also exceeds France, with 9.6 billion m3 of lumber. 

With a production capacity higher than that of France, and markedly more competitive prices, foreign competition is growing. Only seven French companies make Cross-Laminated Timber (CLT), which is commonly used in the construction of wood buildings, despite it having been invented in France in the late 1940s. 

Additionally, although forests are growing, they are not regenerating quickly enough, either naturally or through planting: large game, the hunting of which is heavily regulated, have multiplied over the last forty years (deer and roe deer by eleven, boars by twenty), eating or trampling on seedlings and stripping the bark from trees. 

As noted by Fabrice Denis, VP Strategy, Wood Construction at Bouygues Bâtiment France Europe, “while forests are suffering the consequences of climate change, they also offer a response to it. (...) Lumber can help reduce emissions by 10%; and growing demand downstream will pull the supply side along with it.” 
The upcoming environmental regulation (RE 2020), the 200-million-euro relief package announced by Julien Denormandie on 22 December 2020 (which was developed to protect forest resources and plant 50 million trees), and the 70-million-euro Wood Fund created by BPI France, should allow the industry re-organise itself more smoothly.

On 14 December 2020, its Strategy Committee announced a new “2030 Timber Plan”, “to accelerate the diversification of materials and the reduction of carbon emissions”, which it will present in early 2021.
“The wood industry is in the process of opening up to all stakeholders in the construction industry, to share its expertise and discuss constructive practices in the ecological transition. Far from being dogmatic, it is available to all stakeholders who wish to commit to building carbon neutrality. The challenge for RE2020 will also be to ensure that this family of ‘builders’ becomes acculturated to including materials that can store or be used as a substitute for carbon. The wood industry will support and facilitate this change”, it announced in its press release. 


Joint interview with FABRICE DENIS, VP Strategy, Wood Construction at Bouygues Bâtiment France Europe, and MARC FRANCO, Director of Coldefy Paris and the architect in charge of Novaxia’s Wonder Building project, which is being built by Bouygues Bâtiment Île-de-France – Construction Privée.

How does Bouygues Bâtiment France Europe, a concrete builder, intend to become a leader in wood construction in ten years? Especially since “building with wood doesn’t mean you’re replacing concrete with wood”, as noted by Fabrice Denis, VP Strategy, Wood Construction at Bouygues Bâtiment France Europe. Details below. 

Fabrice Denis, VP Strategy, Wood Construction at Bouygues Bâtiment France Europe


- With the WeWood transformation programme, which has three objectives. The first is to get to a point where 30% of the 600 annual projects of Bouygues Bâtiment France Europe include at least 100 m3 of timber and/or 500 m2 of timber framework by 2030, in order to limit our carbon footprint, since wood, as a renewable material, has the advantage of sequestering and storing CO2. 

Marc Franco, directeur de l’agence Coldefy Paris

Our second objective: to provide a fundamentally different experience to all stakeholders in the industry, since it’s faster, less noisy and less dusty. Five to six fewer lorries are needed to deliver the materials. And since it’s more ergonomic, it offers the possibility of welcoming more women to our sites.
Lastly, wood is great at pushing us to reconsider what we do and how we build. Building with wood doesn’t mean you’re replacing concrete with wood. 

Concrete is poured onto the building site and adapts to all dimensions; all you need is a different formwork. It allows for last-minute arrangements, while wood requires more co-design very early on in the process. Walls, studs and beams aren’t built on site but in the factory, before being brought to the site. As such, the contracting authority has to design the project based on the capabilities of the manufacturers, while considering all of the architectural building trades, since one of the characteristics of wood construction is that you have all these layers laid on top of each other (glass wool, plasterboard) in order to meet acoustic, thermal and safety requirements. 


M. F. – In this 27,000 m2 building, wood is practically everywhere—in the studs, beams, floors, stairs—except the façade, since wood turns grey over time, and this isn’t to everyone’s taste. On the other hand, it’ll be more noticeable indoors, as it’ll be protected by a white surface coating that leaves the wood grain visible. 

The trees on the panoramic terraces that overlook Paris and Bagnolet, or those on the interior patio, will also evolve from season to season and from year to year. 

The occupants themselves will make Wonder Building a bustling and animated space, by taking the staircases that are offset against the transparent façades, which overlook the street and have been turned into usable spaces. Additionally, by making the interior of the building visible to the outside, and by bringing the outside inside, with shops set up on the ground floor, we’ve given the building some potential for interaction between employees and local residents. 


F. D. - We ruled out that idea because it’s an issue of cultural transformation. It’s like when an automaker transitions from petrol to electric, or in Total’s case, from petrol to solar. To carry out this transformation, all of our companies and subsidiaries are learning about wood construction and its challenges. To help them, we created “WeWood Academy”, which offers structured training to all company personnel. 

There’s also “WeWood Community”, a place for employees to share their experiences and pool their knowledge, including with our “WeWood ambassadors”, who are often on the young side; for instance, a new employee who wants to lead a wood construction project in Brest can rely on the experience of a coworker in Lyon. Lastly, we’re going to build a “club” of close-knit partners, with SMEs, startups and architects, in order to develop ecosystems. 


MF. - Being an architect is like being an orchestra conductor: we have an overall vision of the piece, and it’s great when we get to interpret it with highly skilled specialists. We’ve been working together for twenty years, and I appreciate their expertise. These are major building professionals. They have a pretty incredible strike force, with specialised engineers. What we’re lacking in our industry is training. When they pass down knowledge, they do it in the field, between specialists and novices, between seniors and juniors. It’s a pleasure to see that on the worksites.

Fabrice Denis
VP Strategy, Wood Construction at Bouygues Bâtiment France Europe
"Our first priority is to learn how to build with wood, conduct training, and acquire engineering resources. We’ve set up a Centre of Excellence with thirty expert engineers, all of whom are passionate about the subject—they’re practically activists! It’s a pleasure to be able to guide these young men and women, as they want to change the way we look at things."


F. D. -
Our second priority is to make sure that the wood comes from sustainably managed forests, and that all our wood is PESC- and FCS-certified. WWF is supporting Bouygues Construction towards responsible wood sourcing. The third is to focus on local supply chains and jobs, and to use wood from the region whenever possible, or French wood, even if it ends up costing us more. We’re also in the process of developing framework agreements that require a certain percentage of French wood in our buildings. Every call for tenders is an opportunity to build ecosystems, since it’s in our long-term, collective interest. 

On 17 March 2021, Bouygues Construction renewed its partnership with WWF France. Read more here.

The wood demand shock will lead to better forest management and stimulate the French wood industry. There are 400,000 jobs in the French wood industry, and 1,200,000 in Germany! 
Demand will also accelerate research. For instance, we’re pushing around ten R&D programs, including one with a laminating company in Normandy to make glue-laminated beech wood that can be used in studs, beams, floors and shells. 


F. D. - The demand is exponential. In 2020, it was three times higher than in 2019. The hygroscopic health benefits of wood have been proven: in a wooden hospital, people receive faster treatment, and their heart rates decrease. Wood creates a soothing environment. It also allows for amazing architectural shapes, not just high-rise buildings. Investors and users also care about the carbon footprint of construction.

of CO2 emissions avoided
A wood building avoids 60% of a concrete building’s CO2 emissions—20% with all trades included.

F.D. - While a wood building is more expensive to purchase than a comparable concrete building, the overall cost is lower over time, as it saves on heating and is easier and more expensive to rent, which brings in additional revenue. 

M. F. - Yes, there’s a lot of interest in wood, as more people come to realize the kind of state our planet is in. But we need to be sparing with the materials, whether wood, concrete or steel, and avoid overusing any one of them.  


F. D. – Future buildings will be more hybrid and flexible. Wood allows you to modify the building over time, so that it can adapt to subsequent changes in lifestyles. Construction methods such as screwing allow you to more easily reconfigure the interior space than in a concrete building, whose connections are made of reinforced concrete. This also contributes to users’ mental comfort, as it allows them to experiment with a new, more reassuring type of housing, against a sometimes-stressful backdrop of urban densification.  

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Contact : Virginie ALONZI
Foresight Director - DPMS - Bouygues Construction SA
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