Timber construction accelerating in France

In Rueil-Malmaison (Hauts-de-Seine), in the heart of the future Arsenal eco-district, the Petraea residence stands out. Tomorrow, it will blend in with its surroundings: once completed, “We will hardly imagine that it is made of wood”, ensures its designer, architect Jean-Michel Wilmotte. Now under construction, its three six-storey buildings already erected still reveal their solid wood structure, while around the cranes still erect the other concrete buildings in the district. Above all, here, the ears are at rest: no jackhammer is necessary to install the pipes of the different networks. These are simply stapled to the structure before being camouflaged by a covering.

Residential residence, vast set of offices-shops-housing, cultural equipment, office building: wooden constructions are flourishing almost everywhere on the national territory. Ile-de-France is not to be outdone: in Paris, Ivry-sur-Seine (Val-de-Marne), Neuilly-sur-Marne (Seine-Saint-Denis) or even Meudon (Hauts-de- Seine), wooden buildings rise from the ground.

A “niche market”

In five years, the timber industry has made significant progress in construction techniques. New manufacturing processes, such as cross-laminated timber (CLT, for cross laminated timber), have seen the day. And, site after site, the industry has developed solutions to eliminate the risk of fire or even reduce the problems of acoustics.

“Timber construction is still a niche market, particularly in terms of housing”, recognize, however, in unison Olivier Wigniolle, Managing Director of the Icade real estate group, and Loïc Daniel, his counterpart at Nexity Immobilier – these two companies, along with Woodeum, constitute the top trio of operators in low-carbon French construction in 2020. – this represents barely 4% of new housing in Ile-de-France, against a little over 6% nationally. According to a recent survey by the inter-professional association FIBois Ile-de-France (IDF), however, timber construction projects mainly concern housing (51%).

Last November, at the initiative of FIBois IDF, twenty-eight developers and project owners signed a pact, each committing to carrying out up to 40% of new constructions or renovations in wood and / or other biobased materials. (for a total area of ​​1.2 million square meters) by 2025. An objective that the players have no doubts about reaching, especially since the new environmental regulations for buildings – known as “RE2020” – must enter in force in January 2022. However, a real lifeline, this gives pride of place to biobased materials such as wood, which store carbon rather than emit it. It aims to add to the calculation of energy efficiency the consideration of the carbon footprint of the building throughout its life cycle.

Cleaner sites

“With regard to carbon, wood has undeniable advantages”, underlines Hélène Genin, General Delegate of the Association for the Development of Low Carbon Buildings (BBCA), a pioneer in taking carbon into account in buildings. “On the one hand, in its manufacturing process, it has very low emissions, because it is little transformed and requires little polluting energy. And on the other hand, it stores the carbon captured by the tree in the forest, allowing the building to preserve this carbon sink during all its decades of life. “ Over its entire life cycle (construction, operation), a traditional new building emits an average of 1.5 tonnes of CO₂ per square meter. A building that maximizes the use of wood, especially in structural work, can reduce its emissions by 15% to over 45%, and store up to 200 kilos of CO equivalent₂ per square meter, throughout its service life.

“With wood, we go up one floor per week, against one floor per month for a concrete construction”, Julien Pemezec, President of Woodeum

The advantage of wood also lies in the speed of construction and the reduction of its nuisances. Prefabricated in the workshop, the construction material arrives as a kit on the site, in the form of beams and panels pre-cut to the right size, which only need to be assembled. This prefabrication reduces construction time. By generating less waste, less dust, and requiring less water, construction sites are cleaner and quieter. “We divide the number of truck rotations by eight. And by two the time of the shell, which saves four to six months of work, emphasizes Julien Pemezec, President of Woodeum, promoter of wooden buildings since 2014. With wood, we go up one floor per week, against one floor per month for a concrete construction. ” Without counting, notes the architect Philippe Chiambaretta, that “If, in the more or less long term, we want to demolish a wooden building, it is easier to recycle its beams and floors, because we dismantle it, whereas a concrete building is destroyed”.

A downside, however, to the ecological virtues of the site: the wood used is still often imported from Germany, Austria or Scandinavian countries. Not that France does not have the resources, with its 17 million hectares of forests. French sawmills are now increasingly able to supply posts, beams and frames. On the other hand, the offer of CLT-type solid wood panels (used for walls and floors), which did not exist in France until 2016, is still insufficient, although it is gaining momentum. “The processing industry must be further strengthened if we want to avoid that the interest of wood in terms of carbon is penalized by the fact that it comes from far away”, notes Loïc Daniel, from Nexity Immobilier.

Mix of materials

For Philippe Pelletier, president of the Sustainable Building Plan, “Wood construction will really turn a corner when France has a complete and solid wood industry”. And this one to observe: “Wood could be king in building renovation and insulation operations, but this is far from being the case today. “ This market, like that of extensions and elevations, will develop, assures Olivier Wigniolle. Because “Wood is virtuous: it has a strong insulating power. And in lifting operations, it’s almost 40% less weight ”.

To expand their outlets, all rely on a mix of materials and construction techniques. Already, in most buildings with a wooden structure, the foundations and the ground floor as well as the cores of the elevators and staircases remain in concrete. In addition, the exterior facades must, for questions of durability and fire safety, be protected by cladding. “The future is wood, but combined with concrete, steel, terracotta, stone… for some parts of the building and not others, notes Loïc Daniel. It’s about putting the right material in the right place to achieve the most ecologically relevant designs. We adapt to each case, to the morphology of the building, to its structural constraints, and to customer expectations. “