Thermally modified wood in saunas is becoming part of a new approach to sauna construction in the United States. American company Cambium, together with Finnish Sauna Builders, has introduced Carbon Smart Sauna – a sauna line made from locally sourced wood that might otherwise have been chipped, burned or discarded. The wood is thermally modified using heat and steam without chemical preservatives, and the first commercial installation is already operating in Chicago.
The new project is interesting for more than its choice of timber. It raises a broader question: can the rapidly growing sauna industry use more local materials while reducing long and complex supply chains?
For the US market, this question is becoming increasingly relevant as sauna popularity grows and much of the thermally modified wood used in sauna construction has traditionally been imported from Europe.
What is Carbon Smart Sauna?
Carbon Smart Sauna is a collaboration between US-based Cambium and Chicago-based Finnish Sauna Builders.
Cambium specialises in giving urban and other locally sourced wood a longer useful life. The company works with trees that need to be removed because of disease, damage, storms, construction, urban development or other reasons.
Instead of allowing this wood to be chipped, burned or used for short-lived purposes, the company seeks to turn it into durable products.
For the new sauna line, one of the key materials is American yellow poplar.
After preparation, the wood undergoes thermal modification, changing both its technical properties and appearance.
Why are Americans looking for an alternative to cedar?
For decades, cedar has been one of the most familiar sauna materials in North America. It is lightweight, aromatic and well suited to hot environments.
In Finland and the Baltic countries, however, sauna builders traditionally use a wider range of species. Aspen and alder are common, while thermally modified wood has become increasingly popular in modern sauna interiors.
For American sauna builders, using this type of material has often meant importing it from Europe.
That means longer transportation distances, longer lead times and greater dependence on overseas suppliers.
Carbon Smart Sauna takes a different approach: the wood is sourced and processed in the United States, while Finnish Sauna Builders designs and builds the saunas in Chicago.
From an urban tree to a sauna bench
The origin of the timber is one of the most interesting aspects of the project.
Carbon Smart Wood uses trees that already need to be removed from urban and other environments. Reasons can include disease, damage, severe weather or infrastructure development.
Some of this wood would otherwise be chipped, burned or put to relatively short-lived uses.
Cambium aims to redirect that material into longer-lasting applications.
The wood is identified, sawn, prepared and converted into material capable of remaining in use for many years.
For a sauna, this is particularly interesting because timber has to withstand unusually demanding conditions.
What does thermal modification do to wood?
The wood is exposed to high temperatures under controlled conditions, with steam used as part of the process.
Cambium states that no chemical preservatives are used during thermal modification.
Heat treatment alters the characteristics of the timber. Its ability to absorb moisture is reduced and its dimensional stability improves, making it better suited to environments where it repeatedly experiences heating, humidity, cooling and drying.
The process also changes its appearance, giving the wood a darker and more uniform tone.
These characteristics can be particularly valuable inside a sauna.
Sauna timber has a harder job than it may seem
Sauna walls and benches operate in an unusual environment.
The room heats up, humidity changes, and after use the sauna cools and dries. In a commercial sauna, this cycle can be repeated many times throughout the day.
Wood expands and contracts.
If the material is poorly suited to these conditions or incorrectly installed, repeated thermal and moisture cycles can contribute to deformation and other problems over time.
Choosing timber for a sauna is therefore about much more than appearance.
The first major test is already underway in Chicago
The new material has already moved beyond prototypes and product samples.
The first Carbon Smart Sauna project has been installed at AIRE Ancient Baths Chicago.
Thermally modified yellow poplar was used for the sauna walls and multi-level benches.
The project used 2,107 linear feet of material – approximately 642 metres.
That makes the installation particularly interesting because a commercial spa sauna places substantially greater demands on materials than a private sauna used only a few times each week.
A public sauna can operate for many hours every day.
If the material performs well after years of intensive use, that will provide much stronger real-world evidence than laboratory specifications alone.
The supply chain stays in the United States
Another central idea behind the project is traceability.
Cambium says the timber is sourced in the United States, sawn and thermally modified domestically, while Finnish Sauna Builders designs and builds the saunas in Chicago.
The companies are therefore attempting to establish a more local supply chain.
This can reduce dependence on imported thermally modified timber while also shortening delivery times.
For the new product line, an estimated material lead time of approximately two to four weeks has been announced.
Thermally modified wood in saunas is about more than design
Thermally modified timber has become popular in contemporary sauna interiors partly because of its darker and more consistent appearance.
It fits naturally into modern sauna architecture.
But the American project broadens the discussion.
The question is no longer simply what the wood looks like, but also where it grew, why the tree was removed, how far the material travelled, how it was processed and how long it is expected to remain in use.
That represents a different way of thinking about sauna construction.
Does salvaged wood automatically make a sauna sustainable?
No.
It is important not to turn an interesting material concept into an uncritical environmental claim.
The environmental impact of a sauna is determined by much more than the timber used for its walls and benches.
Building construction, insulation, frequency of use, the sauna heater, energy source, transportation, material lifespan and end-of-life treatment all matter.
Thermal modification itself also requires energy.
Using locally recovered wood therefore does not automatically make an entire sauna carbon-neutral.
However, turning already removed local trees into durable building materials is an interesting approach worth following as the sauna industry grows.
The technology itself is not new to Europe
From a Latvian perspective, the idea of thermally modified timber is hardly exotic.
Thermally modified wood has been used in sauna construction and interiors in Finland and the Baltic region for years.
What is new about the American project is the context.
The North American sauna market is growing to the point where the industry is increasingly looking for suitable materials and production solutions closer to home.
From a European tradition to a local American material
The global spread of sauna culture has often meant Finnish heaters, European thermally modified timber and Nordic design being exported around the world.
Carbon Smart Sauna attempts to change part of that formula.
The principles of the sauna remain.
The heat remains.
The wooden benches remain.
But the material is sourced from a local resource stream.
Thermally modified wood in saunas therefore becomes part of a much broader question: can the growing global sauna industry use more local resources and rely less on transporting materials across continents?
One new product line cannot answer that question.
Much will depend on how these materials perform after years of intensive use.
But the first serious real-world test in Chicago has already begun.
Sources
Cambium – Carbon Smart Sauna is here.
Cambium – AIRE Ancient Baths Chicago.
Cambium – Sauna / Carbon Smart Wood.
Finnish Sauna Builders – information about the Carbon Smart Sauna project.
