Thermowood® remains dimensionally stable as the seasons change – better than corresponding untreated or chemically treated wood. The dimensional instability of wood due to varying air humidity clearly decreases in heat treated products. This is due to the reduction of wood shrinkage, lower equilibrium moisture content and slower absorption of humidity because of heat treatment.

The higher the heat treatment degree is, the more the dimensional instability of Thermowood® is reduced. Even in low degrees of heat treatment (Thermo-S) the dimensional instability is reduced by about 20 %. In a heat treatment class suited for outdoor use (Thermo-D), the dimensional instability is still reduced and is about 40-50 % lower than that of untreated wood.

In the building products of wood product industry, such as doors, windows and floors, Thermowood® offers a good option as raw material for applications where the reduced swelling and shrinking of wood brings significant benefit in both manufacture and for the end user.

Research results

Radial swelling, spruce »
Tangential swelling, spruce »