Cross-Laminated Timber

• Material
  CLT consists of several layers of solid wood (in Europe, these are mostly softwoods such as spruce, pine, larch and fir), which are glued crosswise on top of each other.
• Strength
  Despite its light weight, CLT possesses a high degree of structural strength, which enables the construction of tall buildings. An example is the Mjøstårnet in Norway, which at 85.4 meters was completed in 2019 as the world’s tallest wooden building.
• Fire resistance
  Surprisingly, CLT is highly resistant to fire. If fire breaks out, the surface forms a layer of charcoal, which protects the underlying wood and slows down the rate of combustion.

• Heat storage
  Wood has a very good thermal storage capacity. This contributes to the energy efficiency of buildings, reducing energy costs for heating and air conditioning.
• Construction time
  Construction with CLT is often faster, more ergonomic and less disruptive than with traditional building materials because the individual components can first be prefabricated in a factory and then assembled on site.
• Health
  Several studies have shown that wood interiors contribute to improved air quality and can have positive effects on psychological well-being.

When non-renewable materials have to be replaced, CLT is a sustainable alternative to concrete, brickwork and steel. This is also shown in a study by the European Forest Institute (EFI), which makes the following key statements:

• Compared to equivalent structures made of steel or concrete, timber structures emit 20 to 50% less greenhouse gas over 100 years.

• This means that the construction of timber buildings in urban environments could store between 36.7 and 2495.6 Mt CO2 per capita annually, depending on the scenario and floor area.
• Replacing concrete floor panels with CLT panels could contribute to a reduction in global CO2emissions by an average of 50 Mt CO2e (excluding carbon capture and storage), given the full introduction of hybrid buildings by 2050.

The evidence is quite clear: The invention of cross-laminated timber and its market launch in 1998 represented an ecological milestone. Since then, timber structures in residential and commercial construction have been produced using flat slabs that are dimensionally stable, reliably calculable and possess multi-axis tensioning. 

Despite the dwindling availability of natural resources, the utilisation of production waste offers a sustainable option for meeting the increasing demand for CLT, because CLT production creates large amounts of waste – at least 40% of waste or by-products is generated during the production of boards from logs in sawmills alone.

Additional waste, mainly due to window and door cutouts, is also generated during the production and trimming of the raw panels. A research report by the Technical University of Kaiserslautern shows that the waste generated during the production of the final solid wood components amounts to a further 20%.

To create a high level of sustainability, new ceiling and wall elements must be produced from these waste cutouts. Processing the production waste also results in a more efficient process chain – if the new raw material is processed and manufactured directly at the production site, transport distances are reduced to a minimum.