Thermal treatment has long been known to enhance wood's resistance to decay. In the past, wooden piles were charred before being driven into the earth. The heat treatment significantly prolonged their lifespan.
Modern thermal treatment changes the qualities of wood permanently. In addition to resistance to decay and weathering, the thermal insulation capability and dimensional stability of the wood are improved and distortion reduced. The treatment also gives the wood a beautiful dark tone.
Qualities of ThermoWood®:
Reduced moisture ratio at equilibrium
Enhanced dimensional stability
Enhanced resistance to decay
Improved weathering resistance
All resin eliminated
Reduced splitting strength
Slightly reduced bending strength
Source: International ThermoWood Association