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Thermory increases wood quality through thermal modification

Thermory, which started as a sauna materials manufacturer, has grown to the world´s largest producer of thermal wood and sauna materials in two and a half decades. Right now, Thermory is also leading the green revolution in manufacturing.

“Thermally modified wood is not to be confused with heat-treated or chemically treated wood,” explains Christian Pongratz, Managing Director of Germany of the Estonian company Thermory, a world leader in thermal modification.

“Heat treatment works with temperatures around 55 °C, for example, to kill pests, such as in wooden pallets. In contrast, thermally modified wood is heated to over 180 °C to change its chemical structure,” explained Pongratz. This increases its durability, stability and resistance to moisture, rot and pests. It becomes more versatile for facades, saunas and terraces and retains its natural beauty.

With its non-toxic thermal modification technology, Thermory creates durable and climate-resistant exterior facades, interior wall cladding, decking, flooring and sauna products. “Using only heat and steam, Thermory makes the wood more durable and resistant to high humidity or extreme temperatures,” says Pongratz.

Thermory supplies 50 countries worldwide  

Thermory uses specific parameters for thermal modification depending on the type of wood, its thickness and width. In addition, special sensors and actuators in the thermal chamber computer monitor each batch of wood in production to achieve a consistently high level of quality on a large scale. The wood is “baked,” so to speak: within 48 hours, it is heated to 215 degrees, which reduces the Equilibrium Moisture Content (EMC). A cooling process is then carried out, and the wood is brushed, primed, and painted for decorative or fireproofing purposes, depending on the finish.

Thermory manufactures in nearly 10 factories in Estonia and Finland, which supply more than 50 countries worldwide. The company also maintains two warehouses in the U.S. and one in Germany. Most wood comes from Northern and Central Europe and North America, including ash or aspen, alder or pine.

The wood from sustainably managed forests is PEFC or FSC-certified. “These are two international standards for improving forest use and management, so that wood as a renewable resource finds optimal conditions,” says Annika Kibus, General Manager of Woodhouse Estonia.

Using only heat and steam, Thermory makes the wood more durable and resistant to high humidity or extreme temperatures.
Christian Pongratz, Managing Director of Germany of the Estonian company Thermory

Three extraordinary, exemplary objects from wood

Thermory products are used in airports, hotels and retail stores for commercial, public and residential buildings. “Wood can be used as a building material for almost any type of building,” Christian Pongratz elaborates. “Thermory has the years of experience to know exactly which type of wood can be best used where.”

Larger projects in Germany include the Vabali spas in Düsseldorf and Hamburg, featuring Balinese architecture on 20,000 and 36,000 square meters with numerous saunas, steam baths, pools and relaxation rooms. “Thermally modified wood is perfect for sauna construction because it retains its shape,” says Pongratz.

Helsinki’s ferry terminal was designed to meet the needs of the growing Helsinki-Tallinn sea traffic. Photo: Thermory

A unique and award-winning object is the ferry terminal in Helsinki, Finland, which combines functionality with high-quality architecture and design. The waiting hangar, with its 15-meter-high glass walls, offers a panoramic view of the Baltic Sea. The reflection of the sun through the water and the transparent glass surfaces demand a glare-free design and material in the interior.

With thin slats of pine on the curved, sloping ceiling, it was possible to reduce glare within the large open space significantly. The colour effect of the wood is aesthetic and elegant, and the slope of the ceiling provides a visual impetus to direct the passenger path. “The materials used must be durable enough to keep up with the terminal’s useful life in every respect,” Pongratz explains.

What also counts in using facades is that the woods last at least 25 years without major maintenance measures. This is where cost-effectiveness and sustainability meet. Therefore, there is great growth potential in thermally modified facade wood, especially since it is also aesthetically interesting for architects and planners who appreciate its high degree of prefabrication for modular construction.

Digitalisation in the timber construction sector

“When it comes to finding sustainable solutions to complex challenges, Estonian timber construction companies are regularly requested,” adds Annika Kibus. The timber industry is one of Estonia’s largest manufacturing industries. One in four timber houses exported to the EU comes from Estonia, the largest exporter of timber houses in Europe. The Estonian timber construction industry claims to be the industry with the most certified companies in all of Europe and to have the highest percentage of ETA certificates for timber construction companies, a product performance certificate in the construction industry.

But Estonia is also known as a pioneer of digitalisation, using Industry 4.0 and automation applications for a wide variety of economic sectors – including the construction sector. The country, a member of the EU for almost 20 years, is at the forefront of digital transformation in Europe and is considered the most digital country in the world.

In the Estonian timber construction sector, the digital process chain begins with the assessment of the forest condition and the cutting of the timber, continues with its recording upon arrival at the plant, and ends with its processing in planning and construction as well as subsequent installation – even the maintenance of buildings is being digitised (smart house).

Name: Thermory
Established: 1997
Business sector: wood
Provides: thermally modified wood products
Company’s brands:
– Thermory: sustainable and durable wooden products
– Siparila: Nordic exterior and interior solutions
– Auroom: designer saunas
– VMS Timber: barrel saunas and glamping cabins
Employees: 742 (2022)
Revenue: 149,27 mln eur (2022)
Profit: 10,13 mln eur (2022)
Leading export countries: Finland, USA, The Netherlands, Latvia, Germany, Sweden, Denmark,
Belgium, France


  • To make their ships seaworthy and resistant to the corrosive effects of salt water, the Vikings processed wood with fire.
  • Increasing the performance of woods is still important today to equip them against natural forces and environmental influences. Of course, the modern wood industry uses different processes than the Vikings. It applies heat to thermally modify the wood and make it dimensionally stable to the variations in humidity.
  • Thermal treatment makes it absorb less moisture, making it an ideal material for exterior facades, decking, saunas and underfloor heating. It also becomes less sensitive to pest infestation.

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