ThermoWood has gained recognition as a durable and eco-friendly alternative to traditional wood. It is thermally modified timber, processed using heat to improve its properties, making it more suitable for construction, outdoor applications, and other demanding environments. Let’s explore what ThermoWood is and trace its historical journey from early wood preservation techniques to the advanced technologies we see today.

1. What Is ThermoWood?

ThermoWood refers to wood that has been thermally modified through a high-temperature treatment process, often involving steam and an oxygen-poor environment. This process enhances the wood’s dimensional stability, resistance to biological degradation, and ability to withstand harsh environmental conditions without the use of chemicals.

The thermal modification process typically heats the wood to temperatures between 160°C and 230°C, depending on the desired outcome. This heating process reduces the wood’s capacity to absorb moisture by breaking down hemicellulose and altering lignin structure, thus improving durability and reducing the risk of fungal attacks​​.

The most common ThermoWood products come from softwoods like pine (Pinus sylvestris) and spruce (Picea abies). ThermoWood is widely used in applications where untreated wood would deteriorate quickly, such as outdoor decking, cladding, and sauna interiors.

2. Key Benefits of ThermoWood

Dimensional Stability: Thermally modified wood is far less prone to swelling and shrinking due to moisture changes, making it ideal for outdoor use.

Biological Durability: By altering the wood’s chemical composition, the process makes it more resistant to decay, insects, and fungi without needing toxic chemicals​​.

Eco-friendliness: The treatment involves no harmful chemicals, making ThermoWood an environmentally friendly product.

Aesthetic Appeal: The treatment gives the wood a rich, dark color that mimics tropical hardwoods, adding aesthetic value​​.

3. Early Wood Preservation Methods

Humans have been preserving wood for thousands of years, driven by the need for durable construction materials. Ancient civilizations such as the Egyptians and Greeks recognized the importance of drying wood to prevent rot and cracking​. Early methods included air drying, smoke drying, and soaking wood in natural oils.

In the 18th century, the industrial revolution saw the rise of chemical preservatives, which improved wood’s resistance to decay. However, these treatments came with environmental and health concerns, which led to a search for safer alternatives​.

4. The Birth of ThermoWood

The thermal modification of wood began in earnest in the early 20th century. Researchers such as Stamm and Hansen made systematic attempts to improve wood’s dimensional stability and resistance to decay by heating it. While early efforts showed promise, they were not widely adopted commercially​.

The breakthrough came in the late 20th century. In the 1990s, Finland’s Technical Research Centre (VTT) developed the ThermoWood process, a method that used steam and high temperatures to treat wood in an oxygen-deprived environment​​. This innovation created wood products that were durable, environmentally friendly, and attractive, and marked the true beginning of ThermoWood

5. Commercialization and Global Expansion

ThermoWood’s commercialization began in Finland, with the Finnish ThermoWood Association being established in the year 2000 to promote the technology. The ThermoWood process quickly gained popularity in Europe, particularly in Scandinavia, where sustainable forestry practices were already a priority​.

Today, ThermoWood is widely produced across Europe, with companies like HJT-Holz and SWM-Wood. These companies manufacture large volumes of thermally modified wood for both residential and commercial uses​.

6. ThermoWood in the 21st Century

In recent decades, ThermoWood has become a highly valued material in construction, landscaping, and interior design. Its sustainable, chemical-free production method aligns with global trends toward eco-friendly building practices. With advancements in thermal modification technologies, the market for ThermoWood continues to grow, driven by its proven durability, reduced environmental impact, and aesthetic versatility​​.

7. Conclusion

The journey of ThermoWood is a testament to the evolution of wood treatment methods, from ancient drying techniques to modern thermal modification. As the construction industry continues to prioritize sustainability and eco-friendliness, ThermoWood stands out as a material that offers not only superior performance but also a reduced environmental footprint. With its growing popularity in both residential and commercial applications, the future of ThermoWood looks promising, offering architects, builders, and consumers a high-performance, sustainable solution for modern building needs.