Almost 40% of all CO2 emissions come from the construction industry. If concrete – currently the most widely used building material – were a country, it would emit more CO2 than India. In order to make construction climate-neutral by 2050, sustainable alternatives such as timber are now being considered. The Royal BAM Group is working on a factory where about a thousand wooden houses a year will be made, so that house builders can bid farewell to concrete and steel. The factory should be ready in 2025.
According to Pablo van der Lugt, a timber construction expert at Delft University of Technology (TU Delft) in the Netherlands and author of ‘Tomorrow’s Timber’ and ‘Booming Bamboo’, this could mark a tipping point for timber construction. “More and more builders are realising that things have to be done differently. Almost half of all the material we take out of the ground is used in construction, which in this day and age is no longer justifiable in the wake of climate change. So, this is a step in the right direction.”
Price of timber construction will drop as a matter of course
In his book ‘Tomorrow’s Timber‘, Van der Lugt explores the latest scientific developments in timber construction. According to him, the technique has not only been used by forerunners in recent years, but building with timber is becoming more commonplace. The only disadvantage he sees at the moment is the price. “Given that a CO2 tax has not yet been imposed specifically on building materials, wood is about ten per cent more expensive than non-renewable, fossil-based building materials as far as the cost price is concerned.”
“This is partly because wood is lighter than concrete, so vibrations are transferred more quickly. Especially if you build high-rise flats, you have to take extra measures in this respect. You do not want residents to be bothered by noise from their upstairs neighbours. This is technically possible, but it does involve extra costs. Also, building with timber is still very much under development and is not yet being applied on a grand scale, but if large construction companies switch over, it will automatically become cheaper.
In Scandinavia and Germany, for example, he sees that many engineers are being educated about wood. Dutch (technical) studies still have a long way to go. “This unfamiliarity means that contractors often allow for a larger margin of risk in a timber construction project, but this learning curve is progressing rapidly. As timber construction becomes more common, it also becomes less risky. We know it can be done. And new projects are springing up like mushrooms.”
But just how sustainable is building with wood really? Critics often argue that it encourages deforestation and that the glue used by builders to process wood is unsustainable. Van der Lugt always has to laugh about the ‘glue argument’. According to him, it is the last resort. “It is true that the glue is synthetic – although various bio-based alternatives are being developed now. But the current glue more than meets the EU’s health requirements. To make CLT – cross-laminated timber – coniferous wood boards are glued together in alternate directions. The end product only contains 1 % glue. But this glue does not impede recycling at all. So what are we still talking about?”
Concrete industry must assume responsibility
“This, while concrete is made up of 100 % non-renewable – fossil – material. In the production of concrete, for example, much more CO2 is released. If a building has to be demolished, large pieces of debris often remain. At best, these can be ground up and are largely downcycled for road filler. That is why it is important that the concrete industry also assumes responsibility. Upcycling instead of downcycling by dismantling structures,” Van der Lugt explains.
Just as you can continue to use timber components that have been used in the shell of a building, Van der Lugt adds. “You only have to dismantle it and sand it down. Several manufacturers now offer a buy-back guarantee. That means that if the building is removed, components from these buildings can simply be reused. It’s like Kapla for adults.”
Read more about reusable concrete here.
Nor is deforestation an argument for not building with wood, he maintains. “The biggest reason that trees are cut down in tropical rainforests is to make way for agriculture or meat production. That has nothing to do with timber construction. Moreover, we do not have to go that far to get wood for construction. Europe is made up of about 40% forest and about 300,000 hectares – roughly half a million football pitches – are added each year,” he explains further.
If you compare the emissions from CLT production with those from concrete, it is about 100 kilos of CO2 per cubic meter and 300 kilos of CO2 for concrete, not counting the steel reinforcement. Van der Lugt: “Everything is factored into this carbon footprint, from forestry to all types of processing. From sawing and allowing it to dry, to the machinery, the glue and the transport. Concrete is much more energy-intensive and this figure is even higher for steel.”
Read more about sustainable construction here.
CO2 storage in the city
According to van der Lugt, timber has an even greater sustainability advantage compared to current building materials. Wood stores CO2. About 750 kilograms of CO2 per cubic meter with coniferous wood; with heavier types of wood and bamboo, that can even rise to more than double. “As long as you leave those timber houses standing and reuse the wood and don’t burn it or let it rot, the CO2 remains stored. So, you actually end up with a useful form of CO2 storage that keeps getting bigger as you build more with wood and keep on planting new trees in sustainably managed forests in Europe.”
Then sighing he says: “€2 billion has been set aside for Shell to pump 2 megatonnes of CO2 per year underneath the North Sea. It’s a technical solution that in my view is useless – a waste of money. It is a good thing that we are doing something about the CO2 problem. But by building 20 thousand biobased houses, we would have a CO2 advantage that’s just as large and we would solve the housing shortage as well. What would be the right thing to do? I’d know the answer to that.”
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