Stevens

Thermowood

The photographs of the wood species are solely illustrative and may differ from reality.

The warm character of lumber makes it a popular product for residential houses. Both softwood and hardwood are used for interior purposes, such as interior joinery and flooring. However for outdoor purposes, f. ex. terraces, more often tropical hardwood is chosen or preferred because of its high resistance to external influences. ThermoWood offers a perfect alternative to this usually more expensive product.


ThermoWood is thermally modified timber, for the moment primarily softwood from Scandinavian forests. The heat and steam treatment (without the use of chemicals) turns the lumber into a durable and stable product that is comparable to tropical hardwood. Because of the increased durability, the wood is better suited for outdoor use and the beautiful, fine wood style as well as the enhanced stability make it suitable for interior decoration. A final advantage is the increased insulation capacity of 23 % compared to untreated wood, making the product very suitable for low energy buildings.

The modification method through the input of heat and steam results in different advantages. First of all it reduces the ability of the lumber to absorb moisture therefore diminishing the equilibrium of the moisture content. Secondly a rich brown colour appears of which the intensity depends upon the chosen temperature during the process. Furthermore, as the lumber, after the modification, has a lower UV resistance, a beautiful silver-gray color can be obtained after exposure to sunlight. Finally, because components such as cellulose, hemi-cellulose and lignin are made unrecognizable for mould, this cannot be formed or spread resulting in an increased durability.

In summary, the thermal treatment of softwood has a positive influence on the swelling and shrinkage, the color and the biological durability. These three key elements are adapted depending on the end use of the product as will be explained in the next paragraph.

There is a distinction between Thermo-S (Stability), Thermo-D (Durability) and Thermo-D+. Thermo-S resulting in a durability class III, Thermo-D durability class I/II and Thermo-D+ durability class I. These differences result from a difference in temperature. For Thermo-D/D+, higher temperatures are used thus improving different properties as discussed above, but reducing the bending strength. (These are figures for ThermoWood Pine or Spruce)

This technically advanced product is also environmentally friendly as it turns lumber from European forests into a renewable raw material comparable to tropical hardwood in means of durability and stability without adding any chemicals during the process. In other words, first of all tropical forests can be spared and because of its European origin the ecological footprint is much smaller. Next as no chemicals are used, ThermoWood can be fully recycled or exploited in energy production (combustion).

ThermoWood® is a registered trademark owned by the International ThermoWood Association, an umbrella organization founded in 2000 with different companies as members. Only these members are allowed to use the ThermoWood® trademark. The aim of the organization is to co-operate in research, quality control and promotion, product classification and information.

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