Technical Information


ThermoWood has a high resistance against most fungus attacks. This is due to carefully selected raw materials and a patented heat-treatment process. Hemicellulose changes during the heat-treatment, which means it is no longer attractive to fungi and bacteria. Tests have shown that ThermoWood-D (treated at 212 ºC) has a resistance that is better than impregnated wood of class AB, larch, pine heartwood. According to EN 350-1, ThermoWood-D is classed as resistant i.e Class 2. ThermoWood is resistant to Longhorn beetles, Anobium Punctatum and Lyctus Bruneus. ThermoWood is not resistant to biological growth such as algae on the surface. These organisms derive their sustenance from the surrounding air and cause no structural damage, but they are considered in many cases to be an aesthetic problem. Their growth can be prevented through surface treatments.


Tangential and radial shrinkage is reduced by 50%. Significant reductions in movements result in ThermoWood being less likely to twist or cup itself.

Moisture Content

ThermoWood’s Moisture Equilibrium content is only half the corresponding value of untreated pine. ThermoWood is delivered from the factory with moisture content of 6 ± 2%. This level will change depending on atmospheric conditions. Examples of ThermoWood’s modification of the equilibrium moisture content at different humidity at 20 ºC:

65% RH => 6 ± 2%
80% RH => 9 ± 2%
90% RH => 11 ± 2%


ThermoWood’s density is 350-480 kl/m3 when its moisture content is 6% (typical for RH = 65%, t = 20 terms). The material density is about 10% lower than the density of Nordic pine.


Different chemical changes take place during the heat-treatment process, causing a characteristic smell, which some may find offensive. However, tests show that the emissions giving off this odour contain no harmful or dangerous substances. The smell of the finished product will not be a problem, as it dissipates after a few days.

Effect from Fire

ThermoWood’s reaction to fire is no different to that of untreated softwood. It is possible to treat it with fire-retardant treatments.

Thermal Properties

The thermal conductivity of ThermoWood is reduced by 20-25% compared to conventional soft wood. More information can be retrieved from ThermoWood Associations website in the "ThermoWood handbook."


The colour of ThermoWood is affected by treatment temperature and duration: the higher the temperature, the darker appearance. As with all conifers, colour-variations may occur due to different densities. NOTE: The brown colour will fade quickly in the suns UV light. To avoid this, treat it with a brown-pigmented oil.

Health and Safety

There is little difference in the health and safety aspects of ThermoWood compared to normal coniferous trees. However, there are two distinctive differences between ThermoWood and other conifers; the smell of the material and the dust produced in the treatment of ThermoWood. ThermoWood has a smoky smell, due to chemical compounds known as furfural. ThermoWood has no poisonous or harmful components. If you get a splinter or a needle from

ThermoWood, remove it as soon as possible.


When stored outdoors, ThermoWood should be covered for protection against UV light to minimize the colour saturation of the wood. It should also be protected from contact with the ground to eliminate the risk of degradation. When stored indoors, place sufficient bearers underneath the wood to protect it from bending (appropriate distance should be 600mm). When storing, the end-usage should be considered so that the moisture content is even if used for gluing etc.