Thermal modification
Thermal modification is a well-established technology for improving the dimensional stability and durability of wood. The thermal modification process uses heat and steam to cure the wood. There are no harmful toxins or chemicals used in the process.
The advantages of thermally modified wood are:
- 100 % natural treatment
- Wood is treated fully, not only near-surface as with chemicals-impregnated wood
- Resin free
- Suitable for all climates
- Increased dimensional stability and durability
- Decreased water absorption
- Fewer deformations and tensions caused by humidity changes
- Environmentally friendly and fully recyclable
- Beautiful and rich in colour.
According to the European Standard EN350: 2016, wood species are classified into five durability classes:
| Durability | Durability class 1 Very durable | Durability class 2 Durable | Durability class 3 Moderately Durable | Durability class 4 Slightly durable | Durability class 5 Not durable |
| Durability period | Over 25 years | 15 – 25 years | 10-15 years | 5-10 years | Up to 5 years |
| Wood species | Thermo Ash Teak Ipe | Thermo Pine Thermo Ayous Thermo Spruce European Oak | Thermo Pine Thermo Ayous | Scots Pine Spruce Red Oak | Ash Ayous Beech Maple |
Thermal modification process
Thermal modification is a computer-controlled process that utilizes high heat to alter the dimensional composition of wood. The cellular structure is changed by applying heat without oxygen, which creates a controlled chemical reaction.
We heat the material to a temperature of 180–220 °C. At the same time, we protect it with steam.
The steam protects the wood and also influences internal chemical changes. Unlike chemical impregnation, thermal modification enhances the wood thoroughly, not just the outer surface.
The result is boards that are durable and stable in every sense
Wood is constantly subjected to moisture absorption and desorption. Thermal modification decreases the moisture content to 4-6 per cent. As a result, the wood does not react to changes in humidity as drastically as untreated wood.
That makes it dimensionally stable and the material retains its shape far better than untreated wood. The dimensional stability clearly decreases due to varying air humidity.
This is due to the reduction of wood shrinkage, lower equilibrium moisture content and slower absorption of humidity.
A green and local alternative to chemically preserved wood and tropical hardwoods
Many exterior wood products are treated with wood preservatives – some more toxic than others. The thermal modification process only uses heat and steam to cure the wood.
Thermally modified wood as an environmentally friendly and fully recyclable product is also a good alternative to tropical hardwoods.