Discussing Timber Myths: a dialogue between our ambitions and the facts

Pablo van der Lugt, Daniel Ibáñez, Andreja Kutnar, Jose L Torero, Niels Morsing, Francisco Pomponi, Gert-Jan Nabuurs, Imme Groet, Irene Luque Martin, Arjan van Timmeran, Hans Joachim, Simone Mangili, Djordy van Laar, Irene Garcia, Nico Schouten, Joke Dufourmont

The building industry has a huge impact on the environment, both in terms of greenhouse gas (GHG) emissions and resource consumption. It therefore requires a major transition towards more circular and climate-proof building practices. A key piece of the puzzle may come from an unexpected corner: mass timber systems.

For centuries, humankind has built with timber and other renewable, biobased building materials such as straw, reed, hemp and bamboo. A look at the centres of our medieval cities shows the historical importance of these building materials. However, since the industrial revolution in the 19th century, timber has been largely replaced by non-renewable, abiotic alternatives such as mineral materials (i.e., concrete and masonry), metals (i.e., steel and aluminium) and later on plastics as well (i.e., polyvinyl chloride (PVC) or polyurethane (PUR)). This replacement was the result of high levels of industrialisation, which allowed for the improved and more uniform technical performance of these new materials.

While the high-performance building materials of the industrial revolution have— quite literally—brought us to great heights (think about steel-concrete skyscrapers), they come at a price for our planet. As a whole, the building industry is responsible for 39% of global anthropogenic GHG emissions. The production of abiotic building materials is responsible for nearly a third of this amount—about 11% of global anthropogenic emissions.

In addition to its contribution to climate change, the building industry is responsible for 44% of global material consumption. Considering the current ‘circularity gap’—just over 7% of global materials extracted are cycled back into the economy (02)—this means that by the end of this century, our reserves of economically extractable ores used in the production of metals, as well as oil for plastics, might run out.

As we improve in delivering extremely energy-efficient, sometimes even net-zero buildings, the relative importance of operational energy use decreases in the carbon footprint of buildings. This makes it even more important to focus our attention on the energy and carbon embodied in the construction phase of these buildings, where the increased use of sustainably sourced timber offers an alternative with a considerable positive impact.

Timber partly caught up with abiotic materials in the 20th century as a result of its industrialisation. The development of glulam technologies and engineered panel products such as plywood, medium-density fibreboards (MDF) and oriented strand boards (OSB) allowed a more effective use of trees—by utilising residual flows like wood chips and sawdust—and made the output of the forestry sector more efficient as a result.

Increased sustainable forest management and reforestation efforts have also allowed the sustainable timber feedstock in Europe to grow steadily since 1900. Finally, the introduction of automated methods to determine the strength of timber planks (for example, based on laser scan technology) improved the uniformity of sawn timber in various strength classes. This resulted in an increase in timber frame construction practices in the second part of the 20th century.

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