A new neighbourhood is under construction. Huge, prefabbed pieces of reinforced wood arrive to the construction site, each one cut to specifications predetermined by an AI program. The insulation is so good that a heating system practically isn’t necessary and, strengthwise, the wood composite rivals good old concrete.

Next door, another house is going up, this one made of pieces of clay--sourced nearby--that have been 3D-printed in a factory.

Both houses cost less to build than the once-ubiquitous masonry buildings in Luxembourg, and they cost far less to heat. Oh, and it takes just a few days to assemble their main structures onsite.

Wood: it’s happening

The above is, admittedly, a vision of the future--though only in part.

Wood is fast becoming an attractive alternative to concrete and for plenty of reasons. Most obviously, it stores CO2 and it requires neither tremendous amounts of fossil-fuel-generated heat (like steel does) nor a CO2-emitting chemical reaction (like cement, an ingredient in concrete, does) to create. Many people, meanwhile, are drawn to the back-to-nature aesthetic of wood, particularly as the oil- and plastic-dominated era matures into (hoped-for) obsolescence. Plus, studies have shown that looking at wood can lower your blood pressure.

None of that is new, however. What’s new is that the technology used to construct with wood has finally started to bring the cost down. This, at least, is the contention of François Cordier, CEO of Leko Labs. Over eight years and with a team of 50 people, Leko Labs has developed both a novel type of reinforced wood and an AI-powered software that can optimise how to use it.

That optimisation, i.e. minimising the amount of wood needed, was key for Cordier, since bringing the price down--as well as the value up, since the design results in thinner walls and thus more floor space--is what, he says, will make the difference for contractors. This approach is relatively novel too. As he explains in an interview: “[People] have wasted a lot of materials, even in timber construction, because the calculations are done according to antiquated methodologies and nobody has the proper software--so they are putting safety factors everywhere.” In other words, people buy and use more wood than they need.

Two architects from the firm Saharchitects, Sahar Azari and Stephanie Law, point to other factors that have also brought the price down. “[Building with wood] used to be more expensive,” explains Azari, “because we didn’t have enough labour, enough contractors who knew how to work [with it].” Nowadays this is less of an issue, she adds. “It’s more a matter of the price of lumber versus the price of concrete versus the price of steel.”

“[Wood] is not very energy-intensive,” Law adds, “which is making it a little bit more price-efficient now, compared to concrete and steel, which are very energy-intensive.” A related point, Azari adds--concerning not just wood--is a movement in Europe towards low-tech buildings that rely on traditional designs and insulation instead of on tons of expensive technologies.

Azari also confirms what Cordier said, that building with timber means thinner walls which results in more floor space. “So, imagine that building with timber is 5% more expensive than building with concrete,” she says. “But if you also get 5% more living space…”

Another door that has already opened for wood is the regulatory environment, which, according to the architects, is up-to-speed. Current techniques were developed in Austria some two decades ago, explains Law. “They did enough research back then to create the regulations.”

Currently, the tallest wooden building in the world is a 25-storey tower in Milwaukee, USA, finished in mid-2022. According to the Leko Labs website: “Virtually all steel and concrete above ground in a conventional building can be replaced.”

Wood: it could be happening a little bit faster

Perhaps all that steel and concrete can be replaced. But it hasn’t been.

“We can change this industry,” Cordier declares, citing as proof that Leko Labs has signed a major contractor in Luxembourg (CLE) as a client and specifying that the reasons weren’t environmental but cost-related.

Concrete continues to dominate, however. Top-down incentives (like regulations or subsidies) to use wood , nor has the cost tipped the equation strongly in timber’s direction, yet. And without those factors it’s hard-dying old habits that continue to win out.

“The regulations are there, but the culture isn’t necessarily there,” says Law, who reports that many clients still doubt the strength and durability of wood. Azari clarifies that, often, the reaction to wood is positive initially, but then fears set in. Will it rot? Will it fall apart? Will it burn? Certainly not, the architects say, if the structure is designed and built properly.

Here in Luxembourg, wood isn’t part of the building tradition the way it is in a place like Austria, explains Law, adding that the Wood Cluster of Luxinnovation is working hard to change that cultural mindset.

Cordier nevertheless sees change on the horizon, pointing to existing regulation in Sweden and France. “By 2030, if you don’t build in wood in France, you will not be able to construct [at all]--it won’t be feasible [due to carbon footprint requirements].” Some people have put their faith in green concrete, a new type of concrete with a lower environmental impact--but, according to the Leko Labs CEO, this product currently costs twice as much as traditional concrete and therefore won’t be economically interesting.

“It’s going to take a while,” he comments on the shift towards wood, but adds that the market is going in the right direction.

Other materials and methods: someday

Further away on the grand duchy’s horizon are other sustainable building materials such as clay and earth. As of now, no regulations exist in Luxembourg for building with these substances, while in Germany they are currently in a preliminary research and prototyping stage. “As architects in Luxembourg, we are observing it,” says Azari, who already sees potential in rammed earth, a very old method that uses compacted natural materials like earth or gravel. “There are definitely possibilities,” she says. 

3D-printing is another trend being watched and where, in the grand duchy, regulation is yet to arrive. “We are very excited about 3D-printing,” says Azari, “but it’s also very new.” She says we won’t see whole buildings being 3D-printed for a while, certainly not in 2023.

Besides working for Saharchitects, Law teaches at Miami University’s campus in Luxembourg and, in that context, reports that 3D-printing also poses a skills gap: “[My students] have talked about how hard it is to take their computer models and translate them so that the 3D-printer understands it.”

Between regulation, skills and the technology itself, both earthen materials and 3D-printing are further down the road for the construction industry. But the trend seems to be real. Angelika Bocian-Jaworska, who as the founder of the startup Äerd Lab is developing sustainable construction methods, outlined her vision last year: “Imagine living in a house which was built on your site and out of local soil. The walls are self-ventilating and the quality of the air and space is much more human-friendly than generic concrete interiors.”

In her words: “Concrete is passé!”