“Das heiße Thema ist der Brandschutz“
“Einen guten Holzbau zeichnet die Ausführungsqualität aus“
Niko Kumer, R&D manager at Stora Enso for massive timber construction, specifically on the topics of building physics, acoustic and fire safety.
What is, in your opinion, the most relevant information gap and/or prejudice concerning timber construction? Where do you think research is needed?
The biggest challenge that is emerging is the fire safety. There are many knowledge gaps concerning this topic as we have recognized that the methods how we are handling this topic, might not be perfect for describing the behavior of timber. The testing methodologies that we use now were developed for other materials. We borrowed them and applied them to timber. Now several countries are questioning their validity and we all are wondering: should we rewrite the standard?
The second relevant topic of interest is durability. Again, there are not so many answers to the question: “what should we do if, during the construction phase, timber gets wet?” How deep does water penetrate the timber elements, how should we dry it? In the end, the topic of durability is closely related to the quality of the construction and of the construction process. We made a step back in prefabrication when we started to produce CLT. When working with timber frame, walls are delivered on site almost finished and the structure is mounted in days. Conversely, CLT arrives on site as raw timber panels, sometimes it takes week before the roof is covered, therefore it can remain unprotected for a lot of time. CLT production lines are made according to the “industrial thinking”: bring out the greater amount of matter possible, in the fastest and cheapest way, with the consequence, that every small change is slowing down the process. This thinking must change, and future Timber Element factories must be able to produce the most efficient building elements possible, with highest possible value for the costumer, what is definitely more than a naked piece of wood.
In timber constructions, some questions have never had an answer. There is a lot of knowledge available in the country that have an experience in timber construction, but then the market of timber construction blasted – and that unfortunately did not come together with a transmission of knowledge.
In the future, I think we should focus on well-being and sustainability. There is need in research as it concerns Indoor Air Quality in timber buildings. The use of natural materials contributes to good IAQ. It would be interesting to install sensors and to investigate the benefits of having exposed timber in the walls or ceilings in terms of indoor comfort.
What are the technological solutions that are most widely used for large volume timber construction?
Timber frame is very cost-efficient for small buildings. When buildings get higher, additional strength is needed and, therefore, CLT comes in. You can easily assemble 6-storey buildings based on a well-established experience. For wider spans, then ribbed elements start to appear (beams with CLT on top). Timber-concrete composite systems are also popular in Austria, Germany, and Switzerland, taking the advantages of the two construction materials. Then there are hybrid systems with steel frame and CLT elements, or timber frame-CLT hybrid systems, where CLT is used for floors and shear walls and timber frame for all other building elements.
What will happen in the next future of timber construction?
We all know that CLT consumes too much wood. There are solutions such as the ribbed elements that use way less material and achieve the same structural performance. In the future, material saving is going to be a big topic. Timber construction will work because it is the only material that can produce renewable and sustainable buildings. In these days there is a lot of talking about the “Friday for future” initiative: the timber construction goes in the same direction, the call for a sustainable world.
As it concerns the industry, the challenging topic is prefabrication, that allows to improve the quality and to avoid situations in which wood is exposed for long time. If timber buildings have durability problems, the whole sector will suffer from that. Also, prefabrication is not that relevant for all countries. It is important if we want to reach new markets, in countries that do not have strong experience in carpentry. The quality of work is what makes a good timber building, to a great percentage. If material arrivers on site with a higher degree of prefabrication, the construction time is reduced, the return of the investment is faster, the construction site has much less impact and so on… And that also means that the industry can earn more on that, because the products have a higher added value.