Construction sector is already fully committed to wood construction

For years it was hard work for Eric de Munck. As a representative of the Centrum Hout branch association, he repeatedly heard the same reluctance about timber construction during working visits to municipalities, project developers and construction companies. “Always those questions about fire hazard, insulation, availability of the material. And then there was that VPRO documentary three years ago, and suddenly everyone got it.”

De Munck refers to the broadcast of the VPRO program Backlight† In the autumn of 2019, the episode ‘Wood Builders’ was about the potential of wood as a building material of the future. The story immediately buzzed in the sector. “All of a sudden all the quarters fell in the right direction. Clients came to us with questions about how they could use wood constructions, and whether we wanted to think along about a sustainable alternative to concrete,” says De Munck. “All major construction companies now have a timber branch. This is not going away.”

Building with wood has been the practice for some time in Scandinavia, Germany and Austria, among others. In the ‘petrified’ Netherlands, where brick and concrete have been the norm since the war, timber construction is slowly gaining ground. 3,750 new-build homes, 5 percent of total new-build, consisted entirely or partly of wood in 2021.

With timber frame construction, the hull is made of wood, instead of steel or concrete. Because of its lightness, it is especially suitable for ground-level homes and less for high-rise buildings. Of cross laminated timber (CLT), large and sturdy panels of wood layers glued together crosswise, can also be made into buildings with more than six floors.

In addition to the Backlight episode, according to Pablo van der Lugt, wood construction expert at TU Delft, it also helps that a lot of research has been done into wood in construction in recent years. In addition to the environmental benefits, he knows plenty of practical reasons why wood can be a good alternative to concrete. “Wood is five times lighter and can therefore be transported with much less emissions and placed on the construction site more quickly. You don’t have to pour anything and there is hardly any CO₂ and nitrogen free during production. You can also process the wood in a factory manner, which means you can build faster with fewer people and lighter equipment.”

The biggest advantage of wood is that it is a renewable raw material. The softwood used in Dutch construction grows back on its own and forests in Sweden, Finland, Austria and Germany are sustainably managed. In addition, trees produce CO . as they grow₂ record them, and hold them until they burn or rot. Also, hardly any CO . is produced during the production of wood products₂ free. If the tree is processed into planks, the CO₂ as it were ‘secured’ in the wooden construction.

Environmental Score Discussion

Nevertheless, there is a debate among material industries and builders about the environmental score of wood as a building material. According to one camp, wood should score better in the calculation method that determines the environmental impact of raw materials in a building, the Environmental Performance of Buildings (MPG). This includes the CO₂emissions required to make, transport and process the material.

‘Capturing’ CO₂ in wood, however, is not yet included in the MPG score, so that wood as a sustainable raw material misses out on an important advantage, according to the wood industry. For example, it can sometimes happen that a wooden construction gets a worse sustainability score than one made of concrete – while concrete has much more CO₂emissions required during production, plus no CO₂ holds. The consequence of this calculation method is that if a choice has to be made on construction sites between wood and concrete, with an equal sustainability score, concrete is often still chosen instead of wood.

According to the group representing more traditional building materials, the storage of CO₂ in wood ‘temporarily’ because CO₂ released when the building is demolished and the wood is burned.

So the central point of contention is: how long does a wooden beam or CLT panel last in a building construction? According to wood builders and architects, a wooden beam can easily be reused if a house is demolished. This is also in line with the ambition to make the Dutch economy ‘circular’ by 2050, which means that all building materials are reused.

As one of the signatories, Van der Lugt also questions the assumption that construction timber cannot have a second life. “It is frustrating that the calculation is based on the practice that applied ten years ago, but will no longer exist in ten years’ time. Solid CLT is a building material that retains its value. Manufacturers definitely want to reuse that in 75 years when a building is demolished, and perhaps also in the construction afterwards. it could even be reused several times and thus CO . for hundreds of years₂ can save. See the wooden structures in our buildings from the Middle Ages.”

The discussion about CO₂ in wood meanwhile is rising high. At the beginning of last year, about two hundred architects, construction companies and scientists called for a review of the calculation method behind the MPG, and to value wood more ‘fairly’. After parliamentary questions, the then minister Ollongren (Internal Affairs, D66) had an investigation launched into the matter. The outcome is expected at the beginning of May.

Wooden towers and complexes

While the interest groups are discussing the calculation method, market parties do not seem to be waiting for the investigation of the Interior. For example, the Amsterdam Metropolitan Area has already determined that from 2025 at least one in five new homes must be made of wood.

Construction companies have also been switching to timber construction for the past two years. Starting this spring, BAM will be conducting pilots with houses built entirely of wood. The largest builder in the Netherlands is opening a 10,000 square meter factory in Oud-Karspel, where about a thousand timber construction homes will be built by 2025. Heijmans also wants to gradually move towards a thousand wooden homes per year from 2023. Construction group Dijkstra Draisma, Plegt-Vos and three members of construction group TBI also have their own ‘housing factory’, where parts of houses are prefabricated on the basis of wood construction.

Although wood seems less suitable for high-rise buildings than concrete, architects are increasingly coming up with wood-based designs: in Amsterdam East, the first residents moved into residential tower Haut (73 meters) at the end of last year. The planned Sawa residential complex on Lloydpier in Rotterdam (50 meters) is also built entirely of wood. And the partly wooden Dutch Mountains in Eindhoven (100 and 130 meters) will be the tallest wooden building in the world by 2025. In that year, a wooden office tower was also built, which is still a rarity: real estate developer NSI is planning an 86-metre-high office building on the Zuidas, with a construction of solid CLT and laminated wood.

Despite the growing timber construction, concrete will remain the norm for the time being. Even a change in the MPG calculation method will not ensure that the companies switch completely to wood, thinks Pablo van der Lugt of TU Delft. „Achieving the climate goals and reducing CO₂emissions in construction is the most important, and that we can build circularly by 2050. So with both recycled concrete and wood.”