Interview “There is currently more than enough wood in the forest”

Professor Hafner, why would wood be the better building material?
Fundamentally, there is no such thing as the best building material! The most suitable material has to be chosen according to the construction requirements. However, by using more and more wood and wood-based materials, we could reduce the greenhouse gas emissions of the construction sector in the long term. First of all, this means reducing CO₂ emissions and extracting CO₂ from the atmosphere. Wood has the unique ability to do both. Wood that is part of a building temporarily stores carbon, which is only released when the building component in question is disposed of and burned. The longer a piece of wood is used, the longer it can serve as a storage material. In addition, wood regrows and is an alternative to materials from non renewable resources.

Do we actually have enough forests to promote the use of timber in construction?
This is a highly relevant question, and we do take it into account in our research. I have also discussed it with my colleagues on the Scientific Advisory Board on Forest Policy.

We know exactly how much wood is needed for a particular type of building and we can estimate how many new buildings there will be in the coming years. Accordingly, we can calculate the amount of wood needed if a certain percentage of these new buildings were to be built of wood. We link this to statistics on forests. The result of our projections up to 2050 is that there is currently enough wood in the forest for housing construction.

The “H7” in Münster was the first hybrid timber construction in NRW. The load-bearing structure consists partly of wood, partly of steel and reinforced concrete.

© Roberto Schirdewahn

Which wood is primarily in demand?
Coniferous wood. This is exactly what is available in abundance due to the reforestations in the post-war period. The bark beetle and climate change are damaging our coniferous wood forests. Therefore, it would make sense to use this wood to build houses, rather than having to burn it later. Afterwards, the areas should be reforested with a mixed forest that would be better adapted to the local climate.

Since the price of wood is currently at rock bottom, everyone would be happy if there were buyers. It’s just not always easy to find companies that make wooden buildings.

I would always prefer to leave houses standing for as long as possible and renovate them.

No house remains standing forever. How do wooden houses compare to other construction methods when it comes to recycling the building material?
First of all, I would always prefer to leave houses standing for as long as possible and renovate them. Still, recycling should be factored in right from the start of every house construction project. Using fewer composite materials is particularly helpful, as that makes it easier to recycle in the end. In the case of wood, chemical wood preservatives should be avoided so that the material can be reused for other buildings at a later date. If this is no longer possible, the wooden beams can be shredded and processed into chipboard, thus optimising cascading use.

Even if conventional building materials are used, it is important to take into account subsequent disposal or further use at the planning stage.

This is what you teach your students.
Yes, the future generation of engineers should always consider restoration when planning a building. A circular economy is extremely important.

I consider it my duty to do my bit to ensure that future generations will have sufficient resources to live a good life.

You are also involved in political committees in order to implement the results of your research in practice. What is your motivation?
I myself have children and consider it my duty to do my bit to ensure that future generations will have sufficient resources to live a good life. Political discussions on environmental protection quickly turn into polemics. The scientists’ job is to remain objective and provide the necessary facts. Sometimes you have to rein people in: even if timber construction is a sensible thing, it cannot solve all problems. You have to stick to the facts.