possible to produce wood, which does not rot or grow mold, and which
does not vary in size and is environmentally friendly, only by heat
Heat treatment is the computer controlled process of wood heating which
is carried out in a special chamber at a temperature of 190 to 212 ° C,
during which process all the moisture, acids and bacteria in the wood
are driven out.
The heat treatment changes the cell structure of the wood - moisture,
bacteria, and acids are driven out; wood lacking these is not an
environment conducive to the growth of fungus, rot and mildew, and it
resists environmental effects significantly better.
The heat treatment process is divided into three phases: heating and
drying, heat treatment and cooling.
Depending on the wood heat treatment temperature, the heated wood is
divided into classes Thermo-S (S = Stability) and Thermo-D (D =
Durability). Of these, the first heat treatment is carried out at a
maximum of 193 ° C, which adds stability to the wood (wood shrinkage
average 6-8%). Thermo-D, or high sustainability timber is carried out at
a temperature of 197-212 ° C. Thermo-D class timber has only an average
shrinkage of 5-6%. Unlike untreated wooden constructions this timber
does not shrink any more.
The birthplace of the heat-treated wood technique is Finland, where in
research conducted in 1990s the impact of high temperature and steam on
wood was analysed and it was concluded that heat-treated wood has many
advantages as compared to untreated. This manufacturing methodology
started in our neighbour country and now practised by more than 55
companies around the world, including Estonia.