Timber iQ February - March 2020 // Issue: 48 | Page 29

PROJECT
assisted with logistics arrangements by transporting the
project’s material and supplies for the project.
In the end, everything came together with the project being
completed in June 2019. The client was very pleased with
beautiful finishes created by the thermory pine supplied by
renewable sources. The installers were also very impressed
with the ease of working with thermory pine.
"Thermal modification enhances
the wood’s durability and stability
properties, thereby expanding the
range of applications in which the
wood can be used, particularly
outdoors."
THERMORY WOOD: ALTERNATIVE WOOD
TREATMENT METHOD
The method of treating wood with high temperature to make
it more durable was discovered centuries ago. Studies on the
possible benefits of thermal modification of wood began as
early as the 1930s in Europe and US. Decades later, the
Technical Research Institute of Finland became interested in
the idea and as a result, the technique was developed,
innovated and enhanced into the 21st century and for the
past 20 years, world-renowned architects and designers
have relied on thermally modified wood to provide the
ultimate expression of excellence for their exterior and
interior projects. With unsurpassed stability, performance and
rot resistance, combined with its captivating beauty and
elegance, thermally modified wood provides a sustainable
alternative to timbers sourced from endangered tropical
rainforests.
The process of transforming the timber is totally chemical
free. Every fibre of the wood is modified. In special kilns,
lumber is slowly heated to approximately 215°, while
controlling the moisture content through means of steam.
Under the influence of high temperature, the chemical and
physical properties of wood undergoes permanent change.
The end phase of the process is cooling down and re-
moisturising to bring the timber to the normal equilibrium
moisture content of 5-7%, which is suitable for machining,
installing and using.
Thermo-treatment changes wood’s chemical composition.
The depolymerisation of lignin under influence of high
temperature reduces the length of chains of cellulose. In
other words, most of the wood sugars are cooked out,
eliminating the food source for bacteria and insects. The side
effect of this process is change of the colour of the wood
through the entire thickness of each piece. The colour
becomes more sated and homogeneous on all sections and
the grain of the wood effectively comes to light. The effect of
valuable breeds of wood is reached. However, the main effect
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is increase of biological durability. Thermo-treated wood
does not require any chemical protection from rot. The high
heat eliminates conditions for occurrence and duplications of
a fungus or microorganisms. Bio-damaging agents are
destroyed. According to tests thermally modified hardwoods
(such as American and European ash) gain durability class 1
(over 25 years’ service life outdoors), and thermally modified
softwoods (such as Scots Pine or Radiata) have class 2,
which means 15-25 years of carefree lifespan outdoors.
Being equal to tropical timbers in durability, thermally
modified wood considerably outplays them in dimensional
stability. As the result of thermal modification, cellular
structure of the wood is altered to reduce movement related
to moisture absorption. Equilibrium moisture content of
thermory wood is reduced by 50% compared to untreated
wood, and this difference remains after years of exposure,
therefore we can say, equilibrium moisture content of
thermory wood is permanently reduced. Swelling and
shrinkage of wood strongly depends on the absorption
qualities of the wood, and in thermory wood it is reduced
5-10 times for hardwoods and 2-3 times for softwoods.
Thanks to its high resistance to heat and moisture, thermory
is a perfect match for the applications, where wood materials
would normally fail – around pool areas, at waterfronts, in
rooms with high humidity.
Decreased equilibrium moisture content reduces thermal
conductivity. A thermory wooden deck will always be much
cooler in hot summer days than any other decks. Resins are
almost fully removed, which makes the timber very suitable
for decorative coatings. Depending on the type of coating, it
would last 5-15 years without the look changing too much,
thanks to the rot resistance and stability of the wood under it.
Thanks to thermal modification, architects and builders all
over the world have been exposed to a different way of using
timber in construction. Thermally modified wood has proven
its worth in different climatic conditions all over the world.
// FEBRUARY / MARCH 2020
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