Frequently Asked Questions

Unlike in America, European saunas are almost exclusively made from Thermowood. Thermowood refers to wood (typically spruce, but pine and fir can also be used) that has been treated at high temperatures to increase its longevity and durability.

Thermowood is a much more authentic sauna wood than red cedar. In countries where using a sauna is an important tradition and part of daily life such as Finland, Norway, Estonia, and Russia, red cedar does not grow naturally. Instead, sauna makers in Scandinavia and Russia relied on spruce. Spruce was the wood of choice in this region for many years, however, it has an obvious drawback, it can rot if left outdoors untreated.

The Thermal Modification process was invented to overcome this issue! Unlike pressure-treated wood, which most North Americans would be familiar with, thermal treatment is a chemical-free method for creating wood that could be left outdoors for long periods and not rot. The Thermal Modification process also gives the wood a pleasant smell and color similar to red cedar.

During Thermal Modification, wood is placed in a chamber and gradually heated to between 410-450º F. The chamber is completely void of Oxygen to prevent the wood from burning. The wood is then left in the chamber for up to 3 days to allow the heat to penetrate all the way to the center of the wood.

The chamber is a vacuum, so it has to be incredibly strong. An example of a Thermal Modification chamber is below.

The Thermal Modification process is completely non-toxic and only requires heat to function. By contrast, pressure-treated wood is a common choice for outdoor use in the building industry. Pressure-treated wood is soaked in chemical preservatives to prevent infestation and decay. Through thermal modification, we can offer a sauna with the same durability, but without using any harsh chemicals.

The addition of heat alters the wood on a cellular level, and gives the wood a number of technical advantages.

Dimensional Stability

The intense heat dries the wood to the core, removing all moisture and resin. As a result, the wood will no longer absorb water. This reduces the wood's ability to expand or contract, which is a leading cause of water absorption and rot. Further, Thermowood does not react to changes in humidity as drastically as untreated wood (i.e., the risk of swelling, cracking, and shrinkage is decreased), allowing Thermowood to retain its shape better over time. Thermowood also does not secrete sap or resin, even in high temperatures.

Environment Sustainability

The wood used to produce Thermowood originates from well-managed, PEFC-certified forests, and no chemicals or foreign substances are involved during its production. Thermowood is an environmentally friendly material produced by using only natural methods.

Rot and Fungi Resistance

The heating process breaks down hemicellulose, so the wood does not contain the appropriate nutrients to allow rot and fungi to grow and develop.

Increased Longevity

When wood is treated with heat, its average life span is prolonged meaning your sauna will last a lifetime making this the most sustainable sauna product on the market.

Improved Insulation

Wood that has been heat-treated becomes more porous, vastly improving its insulating properties.