Inside the löyly pocket of the Kömmeli loft sauna
The variety of different types of saunas in Finland is amazing. Although a few basic models dominate 21st-century sauna architecture, more exclusive saunas are occasionally created. In this case study, we look into one such project, Loft Sauna Kömmeli from the 2025 Oulu Housing Fair, in which Saunologia was also involved. Loft saunas are special spaces in which heating happens downstairs and the heat and löyly are enjoyed upstairs. The outcome is otherworldly.
Saunologia’s unique sauna case study
According to the Finnish idea of the “Law of Löyly”, one should make saunas so that people sitting on the benches are always have their feet above the heater in a so called ”löyly pocket”, aka. the heat cavity. This may be complicated if you fancy a tall heater and your ceiling height is constrained. But what if you could raise the ceiling?
A specific sauna model has existed in Finland for centuries, known as the loft or two-story sauna, in which the benches are practically on a second floor, on a separate platform. This is associated with agricultural saunas, especially in western Finland in the 19th and early 20th centuries, but the idea is not exclusive to them. For instance, Niemelän torppa’s sauna from the late 18th century inside the Seurasaari Open-Air Museum has this design.
One of the oldest illustrations of the Finnish sauna, from a book by the Italian explorer Giuseppe Acerbi, also depicts a loft-style sauna room structure. Despite its old origins, the model has not died out even as heating technology has been modernized. For example, the 2026 Wallpaper Design Award winner Kaunissaari Puusauna relies on this design.
Designing a brand-new architectural masterpiece loft sauna
I have had the pleasure of visiting several loft saunas during the past ten years of Saunologia. They have, without exception, been smoke saunas or wood-fired heat storage saunas (see, for example, Aitokiuas – keskeytymättömiin löylynautintoihin). However, back in 2024, I learned from the architect Juho Lonkila, with whom we have designed several saunas outside Finland, that he was working on a loft sauna as part of a new private house commission. And what’s more, this sauna would be exhibited as part of the 2025 Oulu Housing Fair, or Asuntomessut in Finnish, which is a major annual event in Finland.
The design challenge regarding the house didn’t come out of the blue, but it was a short one. “Surprise us,” was the brief Juho got from the future residents. Being a long-term friend of the young couple about to embark on the home construction expedition, Juho had some firm ideas about what they might like.
A great sauna would be a top priority for both, so Juho kept it central as the project twisted and turned over the years. This project twisted especially a lot, as Housing Fair participation, with its model of bringing in multiple collaborators, also increases the number of stakeholders and requests to new heights. But through the revisions, the sauna remained.
The sauna design was mostly complete by the time I got involved, but I assisted Juho in finalizing the ventilation plan. We also involved the French engineer Corentin Macqueron, who has also been working with Saunologia, to create a simple computational model of the sauna to assess heater placement and selection. His model turned out to be accurate in predicting what followed, as we get to the end of this story.
Like a moth to a flame
Originally, I thought we could enjoy the Kömmeli steam during the Housing Fair with Juho, but that soon turned out to be impossible for many reasons. However, Kömmeli was a super popular destination from the fair’s first day onward, and many people had the chance to marvel at this unusual sauna in person. Afterward, the sauna even received a recognition award from the Association of Finnish Master Builders and Building Engineers RKL.
But of course, seeing a sauna, even on site, not to mention on social media, is not the same thing as actually experiencing it for real. The idea had been brewing for months after the Housing Fair closed in August 2025. Finally, in March 2026, the opportunity knocked. I made an excuse to travel to Oulu, as Juho and another Saunologia associate happened to be close by. So, on a windy late-winter afternoon, we came knocking at the residence and were handed the responsibility for heating the sauna by the owners.
First impressions
I knew beforehand that we were talking about an exceptionally tall, 3.8 m (close to 13 ft), room that is part of a modern single-family house but has its own entrance. In advance, I had a hard time imagining how that would integrate with the overall setting of a single-floor building, but once I saw, it was all seamless, thanks to Juho’s great design!
The Kömmeli sauna section is almost like a building of its own. It connects with the rest of the house via the outdoor entrance. This means that sauna bathers have nice access to the outside to cool off between sauna rounds. The outdoor seating was still a work in progress at the time of our visit.
Entering the sauna section takes you to a dressing or reading room that already sets a different mood from the rest of the house. There’s an exceptionally tall interior wall with an ingenious door lined with the same interior panelling, blending the door with the wall. The red wall tile begins here. It feels warm thanks to the hydronic floor heating common in modern Finnish houses.
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Rushing to the second floor
From the dressing room, we proceed to the bathroom. This is a narrow space with a shower at one end and the toilet at the other. Only a couple of steps and we are through to the glorious sauna room.
The sauna is organized neatly into two floors. Downstairs is spacious, with the elevated heater, a small wooden hot/cold tub, and the massive stairs leading upstairs. Although the heater is massive and tall, it has been raised off the floor by a concrete structure (75 cm; 30 in). The concrete platform has space beneath the top plate for storing firewood and an air channel for feeding the heater.
But I didn’t stay to inspect all the technical details, as I was rushing up the nine steps to get a feel for the complete space. Upstairs, I find a simple wooden platform and a long bench running longitudinally along the 3.7 m back wall on a single level. This means nice seating for at least six adults. Once you’re up, you’re in the zone! And once you’re seated, you can also admire the view outside from the small window on the side of the stairs.
Technical sauna details
The Kömmeli building itself is made out of massive wood, laminated logs, some of which also make up the sauna walls. The sauna has an area of 9 m2 and a volume of 35 m3, so it is fairly large by all private sauna standards. A “detail” you can’t miss is the massive Finnish Löyly IKI wood-burning stove, which has a total stone mass of close to 400 kg (over 800 lbs) and a height of 95 cm (37 in). Because the space is so tall, we still have about 2 meters (6 ft 4 in) of clearance above the heater. Although the manufacturer has specified the sauna for use in spaces up to 40 m3, it only has a nominal heating power of 17.2 kW, making me wonder how it has ever passed certain Finnish inspections.
Because the heater has its own air feed and the house is modern, the sauna has fully mechanical ventilation. We designed the mechanical ventilation following best practices, feeding fresh air into the sauna high up on the wall above the heater. The exhaust points are on the downstairs wall.
Löyly inside the loft sauna
In modern times, the best, if not the only, reason to build a loft sauna is to maximize thermal comfort by minimizing temperature differences (stratification) from head to toe. This is also achieved in Kömmeli. I brought an array of four RuuviTags to a single spot, at four different heights, to measure how the sauna heats up and how the steam reaches different layers. The temperature difference between the ceiling and the platform floor is less than 10 °C, and it drops only slightly at the lowest measurement point under the platform. The automatic scaling of the colors in the infrared image below gives a slightly misleading idea about the minimal stratification.
The feeling of warmth on the platform after almost two hours of heating is very smooth. Everything feels lovely, evenly warm. Of course, the real fun only starts when the sauna master puts in some löyly. The steam pours over you and under you. Leaning forward doesn’t change things. The only escape is down the stairs! Löyly is administered using an exclusive solution, a water faucet and a shower head! No messing around with a ladle here. The heater gets a shower of high-quality löyly water.
The steam pours over you and under you.
The smooth löyly thoroughly fills the cavity upstairs. Even though the sauna is not very hot, just around 60°C, the presence of löyly does not leave anyone feeling cold. Quite the opposite. The steam tends to hit the opposite corner the most, so we decided to switch places on the bench between the rounds to get a feeling for the different intensities of steam across the bench.
A fulfilled architect
“I am extremely happy to see how satisfied the new residents, Lassi and Emma, are with their new home and new sauna. That’s the only thing that matters in the end. The journey from the lot application through the fair and finally to making it their home has been an adventure,” Juho tells me while we are sitting in the dressing room, waiting for the sauna to heat up.
“I am proud of how the sauna turned out. It is exactly what we were after: the dim atmosphere and the smooth, moist löyly. Just going to the sauna section feels like making a trip away from the daily toil and bustle,” Juho continues.
In explaining the house development process to me, he emphasizes that we are dealing with a Housing Fair exhibit. This means the architect loses control over many details normally under his or her jurisdiction. For instance, here the choice of the sauna heater was reversed at the final moment. The downstairs sections of the sauna were also transformed, but they will likely find their place over time. Despite the small deviations from the grand plan, the architect has reason to smile.
Highlights and lessons
Kömmeli once again proved the point about loft saunas. Rather than fighting physics, it is better to ride along with them. If you get the opportunity to try or build one, definitely go ahead! The thermal comfort inside will be rewarding.
The downside of the loft construction is clearly energy use. Although the downstairs barely heats up, you still have a considerable space to heat. Here, the chosen heater was not optimal. I would say it had way too much stone and too little power, resulting in a very long heating time and moderate temperature. For private, everyday use, it is just excessive. I measured the sauna heat-up and temperature stratification using an array of four RuuviTags (3 regular and 1 Pro). These reveal the challenge, illustrated in the graph below.
With the present setup, there is enormous steam capacity that four guys in an hour can use only a fraction of. And for more serious steamers, hitting, for example, 80°C would have taken about three hours at an average speed of 20°C/h.
I hate to say it, but because of our 2024 computational model, we knew this would happen, as the simulations showed that the heater should be almost twice as powerful as this one (close to the standard 1 kW per 1 m3 rule). However, when designs face reality in a project that has numerous stakeholders, decisions may be compromised. Luckily, the owner can replace the heater with a more appropriate model at any time if they want to heat the sauna faster or to a higher temperature. There is actually even an option to switch to an electric heater.
On behalf of Saunologia, I wish the owners a long and prosperous life with their splendid sauna!
Want to enjoy your own version of Kömmeli? We can help design it!
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Saunologia is the provider of premium Finnish sauna design services for clients worldwide through FinnishSaunaDesign.fi. Led by Dr. Lassi A. Liikkanen, our work combines authentic Finnish sauna expertise, modern design thinking, and technical know-how to create exceptional sauna experiences for homes, hospitality projects, and wellness destinations. From concept design to expert guidance, we help bring world-class sauna ideas to life with credibility rooted in Finland.
