Today Cambium and Finnish Sauna Builders are launching Carbon Smart™ Sauna: a sauna built on thermally modified poplar, made from Carbon Smart Wood™, Cambium's traceable, salvaged, U.S.-milled hardwood. It is designed and built in Chicago by the team at Finnish Sauna Builders, and it is available now.
For years, U.S. sauna builders who wanted thermally modified wood bought it from Europe and waited three to four months for it. Finnish Sauna Builders, one of the largest sauna manufacturers in the country, is now bringing Carbon Smart Wood™ to the sauna market, with a dedicated line built on Thermal Poplar: salvaged American hardwood, heat-and-steam modified, delivered in two to four weeks.
The default has a problem
When you picture the inside of a sauna, you probably picture cedar. In North America it has been the default for decades. In Finland, where sauna comes from, cedar is rarely used at all. Saunas there are built with low-fragrance woods, and increasingly with thermally modified wood. Cedar's scent is strong and permanent, and in a room you sit in for an hour at a time, it isn't something you can turn down.
That matters more than it used to. Sauna is no longer a niche finish detail. It's a line item on hospitality, multifamily, athletic, and corporate projects, and on more residential ones every year. The material conversation hasn't kept up.
Lately the alternative to cedar has been thermowood shipped in from the Baltics. Both work. But neither is made here, neither arrives in under two months, and neither comes with the documentation your projects now have to show. Cedar carries a 30% tariff and eight to ten weeks of lead time. Imported thermowood carries the tariff plus duties and shipping, and twelve to sixteen weeks. Both are being reassessed on embodied carbon, IEQ, and supply chain reliability, and the reassessment keeps landing in the same place: the sauna needs a wood that's made here.
Heat, held by the right wood
Every traditional sauna wood, from aspen to alder to cedar, is light, low in density, and free of resin, so it won't scorch bare skin at 180°F. Yellow poplar sits in that same family: straight, even grain, no pitch to bleed, no scent to sit in. What it never had was durability at sauna temperatures.
Thermal modification gives it that. Heat and steam, held at temperature for a set period, change the wood itself. They drive out the moisture and the sugars rot feeds on, so the board stays dimensionally stable through daily cycling between wet and dry, hot and cold, and resists decay without a single chemical. Nothing to off-gas in a hot room. The same process turns the wood a deep, even brown, the tone modern sauna design is built on, without cedar's variation or the yellow cast of imported thermowood.
The same board goes into a private home sauna and a hotel spa running fourteen hours a day, and it holds up in both.
Why Finnish Sauna Builders
A material is only as good as the room it's built into. Finnish Sauna Builders has spent nearly fifty years, since 1977, designing and building saunas for architects, developers, and homeowners across the country, and they know what a sauna wood has to do that a decking board never will: hold its shape through thousands of heat cycles, stay comfortable under bare skin, and look right for decades.
Cambium sources the wood and mills and modifies it through its network of U.S. partners. Finnish Sauna Builders designs and builds the sauna. Every Carbon Smart™ Sauna is built in Chicago and ships from there.
Already in service
The first Carbon Smart™ Sauna installation is at Aire Ancient Baths in Chicago, a thermal spa that runs its saunas through the kind of daily cycle that finds the weak point in any material. The room is lined floor to ceiling in thermal poplar, with tiered benches wrapping three walls and three glass walls opening onto the outer room. 2,107 linear feet of material went into the cladding and benches.
Made here, start to finish
Like all Carbon Smart Wood, the poplar comes from salvaged sources across the United States and is milled and modified by Cambium partners in Northeast. The supply chain is entirely domestic, which is why the lead time is measured in weeks, and it keeps revenue with the landowners, arborists, mills, and transporters we work with in regions across the country.
Specifying it
Carbon Smart™ Saunas are available now through Finnish Sauna Builders.
- Species: Thermal poplar is the recommended sauna species. The full Carbon Smart Wood portfolio is available, and any species can be prepared for sauna at the right moisture content, so the same wood can carry into benches, decking, and millwork throughout the space.
- Profile: Fine-line / nickel-gap cladding and bench stock.
- Treatment: Thermal, chemical-free. Heat, steam, and time.
- Provenance: Salvaged and under-utilized U.S. hardwood, [full chain of custody]
- Lead time: 2–4 weeks.
Request a sample or start a project at finnishsaunabuilders.com/carbon-smart or cambium.com/contact.
Learn the material
On Wednesday, September 30th at 11am PT / 2pm ET, Alex Layoff and Allison Palmer will present Designing the Modern Sauna, a free one-hour course for architects, designers, and specifiers covering thermal modification, species comparison, embodied carbon documentation, and sauna detailing.
