What is ThermoWood®?

The thermal treatment process of ThermoWood® has been patented in Finland, and the pioneering method has been tested and approved by VTT (Technical Research Centre of Finland).

It is an ecological and alternative method to, for example, pressure treatment of wood, allowing for significant improvement of wood properties, often attributed only to rare or expensive exotic species. During the thermal treatment process, which lasts about 96 hours, no chemical substances are used.

Thermal modification significantly improves the properties of wood, its resistance to decay, and reduces its susceptibility to swelling. It results in better dimensional stability and thermal insulation (by about 20-25%), the wood is resin-free and hygienic. ThermoWood® is more durable than natural wood in a wet environment. All these features make it one of the best materials for the production of saunas and hot tubs.

ThermoWood® creates a welcoming atmosphere with its warm texture, color, and gentle velvety structure.

Products made of ThermoWood® offered by Vingberg are crafted from the highest quality selected Scandinavian wood.



    No environmental or health hazards, does not emit formaldehyde or any other chemical substances.


    During the production process, no chemical additives are used; the material is environmentally friendly and recyclable.


    Retains its shape much better than ordinary wood, with susceptibility to swelling, twisting, and bending reduced by 90%.


    Maintains its durability in all weather conditions, more durable than ordinary wood in a wet environment.


    Provides 20-25% less heat loss compared to ordinary wood.


    Low moisture content completely protects against insects, resistance to water, fungi, and mold.


    Bacteria are eliminated during the heating process.


    During the thermal modification process, resin is completely removed from the wood.


    The heat treatment turns it into a dark, uniform color throughout the cross-section.


    Due to its lower UV resistance, wood exposed outdoors without an oil or stain coating will develop a noble natural gray-silver patina over time.


    It better holds paints and varnishes on its surface compared to ordinary wood.


    By subjecting the wood to the thermal modification process, the boards become lighter by up to 20%.



Finnish pine ThermoWood®, used in our saunas and tubs, is highly resistant to outdoor conditions and requires no maintenance, provided we allow for the possibility of it turning gray. However, most of us prefer the warm, noble, brown hue that we see on the day of delivery. According to the usage and maintenance instructions, to preserve the original color, regular maintenance (1-2 times a year) is very important. Coating the boards with colored or pigmented wood oil, wax, stain, varnish, or paint that contains UV filters helps protect against pollutants and maintain the aesthetic appearance.

The ThermoWood® surface should be protected before or immediately after installation. This will ensure the preservation of the beautiful brown color. Any excess substance should be carefully wiped off. Always adhere to the manufacturer’s recommendations for the applied substance.

Surface protection should be renewed as needed. Subsequent maintenance should be carried out at time intervals dependent on the climate, intensity of use, and level of exposure to UV radiation. For regular wood painted with an opaque varnish or paint, the typical interval between surface maintenance is 5 years. For ThermoWood®, this period can be significantly extended, up to three times longer. By using a more stable material, significant cost savings in the maintenance of terraces and facades can be achieved over the entire product lifespan.

ThermoWood® boards are brown in cross-section, so even if they have not been coated with oil for an extended period, it is possible to restore their original appearance. However, it is worth remembering that regular wood protection is much less labor-intensive than cleaning and renovating its coating after an extended period.

VINGBERG has been conducting analyses and research for many years on various protective coatings for ThermoWood® wood. As a result, he recommends the Austrian Adler Bodenöl ThermoWood oil – a high-quality oil with a properly selected pigment, containing a UV filter that penetrates deep into the wood structure and preserves and emphasizes the beauty of ThermoWood® to the highest degree.


The surface of indoor wood can be protected using regular paints, wood oils, waxes, and varnishes. In saunas, a protective substance with the addition of paraffin oil can be used to enhance the color of ThermoWood® and protect it from contaminants.

ThermoWood® without surface protection

All wood materials are characterized by the fact that over time, small cracks and splinters may appear on their surface. While ThermoWood® is less susceptible to such damage, the risk still exists, and proper coating provides excellent protection. Therefore, it is recommended to protect the surface of ThermoWood® whenever it is exposed to atmospheric conditions.

If the surface of ThermoWood® is left unfinished or coated only with wood oil without pigment, the brown color will fade, and over time, the surface will turn gray due to UV radiation exposure. The gray color of ThermoWood® exposed to atmospheric conditions is elegant, and its excellent resistance to decay remains unchanged. However, horizontal planed surfaces such as terrace decking, which are exposed to wear, rainwater, and sunlight, require the application of a protective layer to ensure long-term use and proper mechanical properties. In general, covering surfaces with wood oil, for example, is the best way to protect wooden decking. Furthermore, the applied layer protects the wood from airborne contaminants and makes it easier to clean.

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