Europe's largest wooden campus prepares to open in France

“Here, we wanted to give the stairs the leading role”: the phrase is not trivial to present wooden buildings, not far from the forest of concrete towers of the La Défense business district, to the west of Paris, where elevators normally serve as places of conviviality.

The Arboretum district, which is to be delivered soon in a 9-hectare park on the banks of the Seine, wants to break the codes.

It presents itself as the largest solid wood tertiary campus in Europe, supported by the real estate company WO2, a developer specializing in "low carbon" projects whose shareholders are Quebec pension funds, the Caisse des Dépôts or the insurer Allianz.

In addition to two old industrial buildings made of concrete and brick - former Smurfit stationery factories recycled into a sports club and conference center - the complex has five new office buildings of seven to eight floors, whose facades are striped with wide staircases of wood flying from terrace to terrace.

The investment amounts to some 550 million euros to finance in particular 20.500 cubic meters of laminated wood, "as strong as concrete", or a small forest.

The material is not local. It comes from Austria, delivered by the Finnish-Swedish company Stora Enso. No French player had the industrial capacity to deliver this. Even for the more familiar Stora Enso, this is the largest all-wood real estate project ever carried out, says Lars Völkel, the German boss of the materials group's wood division.

To bind the boards, “we only use durable glue that has no effect on health,” he assures.

Not yet zero carbon

“Wood, coupled with geothermal energy for heating and the reuse of materials for certain exterior paving, allowed us to halve the carbon footprint of the complex compared to a classic concrete project,” says Guillaume Poitrinal, founder of WO2, which nevertheless recognizes that there are "still efforts to be made to achieve zero carbon".

“This type of building could exist everywhere in Europe if standardized legislation like that adopted in France were developed,” notes Mr. Völkel.

The visit to the site organized for the press before its inauguration coincides with the holding in Paris until Friday evening of the first "Buildings and Climate Forum", intended to review ways of building globally to decarbonize the construction sector, while by making buildings more resilient to climatic hazards, including heatwaves.

The Arboretum complex meets the new RE2020 construction standards, in force since January 2022 in France, the first country in the world to adopt climate rules of this level, which evolve over time.

“We are asked for performance in energy consumption and CO2 emissions over the entire lifespan of the building, from its construction to its disappearance, and we are left to find the technical solutions” explains Mr. Poitrinal. According to him, concrete, which emits very high amounts of CO2 which warms the planet, must be reserved for heavy infrastructure such as underground passages, dams or bridges.

Here, the buildings rely on a certain simplicity, without false ceilings or gimmicky green roofs, but there is a vegetable garden and an orchard at the foot of the towers. The parking lots are supposed to accommodate 1.400 cars and 1.600 bicycles.

For the moment the garden is still sleeping in its winter mulch. A few artichoke plants emerge. “We see sparrows and tits arriving,” rejoices the gardener.

It remains to be seen that tenants arrive. A delicate task when entire towers are empty a few hundred meters away.