The one thing that always comes up when people ask me questions about building saunas is “How do you insulate it?”. Intuitively, one might think that the sauna, with it’s high temperatures, would need more insulation than a house and should be as tight as possible to conserve energy. In fact, I’ve had building inspectors give me a confused list of requirements using such logic. The reality is that a sauna is such a different beast than a living space that most energy efficiency related calculations have to be thrown out the window. R-value, the number printed on most insulation products, is the resistance to heat flow of a given material of a given thickness for a given temperature difference (delta T) between the hot and cold side of the material. Typically, in our region, delta T is assumed to be 35° F, but in a sauna, the delta T might be 165°! So, in terms of heat loss, we get some very different calculations. To really understand R-value, you need to think in terms of it’s inverse: the U-value, or coefficient of heat transmission. U-value is expressed in units of Btu/hr/sq. ft./°F, or, plainly, how much heat is lost per square foot for every 1° temperature difference. A typical sauna, with R-13 average insulation, might lose 4000 Btus per hour (or 1200 watts). But, a typical sauna stove generates 25-40,000 Btus of heat per hour, so losing 4000 Btus is not a big deal. (It is more important if you use an electric heater: an 8 kw unit can only put out about 20,000 Btus an hour.) The other factor to consider is that, unlike a living space, you are not trying to hold the heat for very long. So, you don’t need to stack up piles of insulation in the walls and ceiling. In fact, many old saunas had no insulation at all.
What R-factor does not measure, though, is radiant heat flow. Radiant heat is like the sun warming your face; it is the short wave radiation that you feel. At higher temperatures, short wave radiation becomes a bigger factor than convection. To contain that radiant heat, we use foil (think thermos bottle or emergency blanket), but foil, being highly conductive, only works if there is an air space between it and the heat source. The foil doesn’t have to be visible to work; it can be buried between other layers of materials. In my saunas, it is behind the cedar, with an air gap between.
Saunas are also not meant to be tight, stuffy boxes. They require airflow to move the heated air and steam and to make them comfortable. The old sauna at Podunk was the best one around because it was old and drafty and it always smelled fresh. Counter to today’s high-tech homes, ventilation has to be designed into the sauna room to let it breath passively. The trick is to do it without creating annoying drafts.
When you sit on the bench and enjoy the relaxing warmth of the sauna, you probably aren’t running all of these calculations through your head—and neither am I! What I do know, from forty years of sauna experience, is what does and doesn’t work. Mostly, you want a good pile of rocks (kiuaskivet) that are hot enough to alternately bask you in their radiant heat and make good steam (löyly) and convective heat off the heater (kiuas) to produce waves of heat that gently wash over you as you breathe in the fresh aroma of the sauna. You want air, some light, and a feeling of openness and connection to the outdoors. It’s not so much science as it is art or perhaps a melding of the two.
If you do have specific questions about designing your own sauna, feel free to give me a call or email. Or better, have me come over for a consult. If you live far away, I can do one-hour phone consults. In my sauna building classes I talk about all the science and art of saunas in greater detail.
Recently, I was called upon by a couple who had bought a property with an existing sauna that needed some professional help. The structure was a cordwood affair: a building method where timber-framed walls are in-filled with short logs, stacked like firewood, with mortar between them. It looked like it came right out of the pages of Rob Roy’s classic how-to book: The Sauna. The exterior was fairly solid and quaint in a hobbit kind of way, but the interior, in terms of functionality, had some serious flaws. The timber frame and log and mortar walls looked pretty good, but it was obvious that the project is a classic DIY affair: a case of a homeowner taking on a project that looks easy but with complex details that get skipped due to a lack of knowledge, funds, or basic skill.
There are elements to a sauna that are essential: such as a welded-steel stove that will not crack or explode when doused with water and installation that conforms to the NFPA 211 guidelines. Insulation must be able to take the heat, provide proper moisture retention, not attract rodents, and not become a health hazard. Doors must open out and have non-metal, non-latching hardware and be self-closing (ever try to turn a 200° F doorknob with sweaty hands?). There must be no varnish or paint in the sauna room; it will only off-gas or worse, burn.
This sauna missed all of these points and more. From the pile of starling skeletons in the stove, I can only guess that it has not been used in a very long time (another detail: birds will fly down the chimney only to find themselves in a death trap), I can only guess that it had not been used in a very long time. From the lack of tell-tale scorching or smoking of the wood, I could also tell it had not been used much. In fact, if it had been fired to a decent, Finnish-approved temperature, I am sure it would have either caught on fire or sent its users scrambling to get out as all of the varnished wood off-gassed.
It is a classic example of a DIY affair: started with good intentions but never finished properly. When I went into the house with the owners to discuss my plans for bringing it back to life, they brought out a book that had been left with the house: a dog eared and highlighted copy of Rob Roy’s book The Sauna.
I just completed my second mobile sauna for a client and brought it home to give it a test run.
The premise is simple: take a small trailer and build a sauna right onto it so the client can move it back and forth between their lake house and their regular house. As simple as it sounds, the challenges to pulling off such a project are many. First, creating a roomy design for a 5’x8′ space without creating a claustrophobic box takes some planning. A big window with a generous view really helps. So does the gently arched roof—which means that even a tall person doesn’t have to stoop. And the white cedar I use creates a world of it’s own. Upon entering the sauna, you are bathed in the aroma of the north woods. The color and gentle pattern of the grain is soft and welcoming to the eyes. It is this cedar, which I get from Northern Vermont, that makes this little vessel possible. It is the lightest North American species, yet it is no weakling. Favored by boat builders, cedar is easy to bend, strong, and stable. It allows me to keep the trailer under its listed gross weight limit. The entire roof structure weighs less than a hundred pounds!
This second mobile sauna is heated by propane with a Scandia heater. The ample rocks make good löyly—in fact, after a few hours, the rocks were still warm when I went out tonight and looked through the sauna window to check out the Moon chasing Jupiter and Venus across the heavens.
Several years ago, feeling a need for a change, I sold my house (and sauna). But the new mortgage rules discourage banks from lending to self-employed folks like me and have kept me in a renters trap. I don’t mind the mobile existence for now, but I do miss my sauna. The trailer sauna is the perfect solution. No matter where I end up, I can take it with me! So, if you are a renter but dream of owning a sauna, there is a solution.
Interior in white cedarMobile sauna by Rob Licht Custom Saunas
Recently, I was visiting my good friend Daniel, in Eugene, OR, and had the fortune of being able to help him put the final touches on the sauna he has been building in the backyard of his urban utopia. He moved there seventeen years ago from Ithaca, leaving behind the sauna on the family homestead in Podunk, just outside of Ithaca (yes, that really is the name of the hamlet). That little weathered building was where I was indoctrinated in the way of the sauna; it was the catalyst behind my sauna building career. As was typical with the Finns, Willie Uitti (the property’s first chicken farmer owner) built the sauna at Podunk was built first and it served as rudimentary shelter while the house was being built. Daniel has had to dream for the past seventeen years before he was able to build his sauna.
We worked together for a day and a half installing the heater, hanging the door, and getting it ready. Needless to say, the first firing of the new sauna was nothing short of perfect. It reached a good temperature, it made good löyly, the reclaimed cedar boards gave off a rich odor, and most importantly, it reached down to the pit of our sauna loving souls and transported us back to that cherished time and place on the banks of Taughannock Creek.
To the Finns, Sauna is not just a building or the simple act of sitting in a hot room, it is a quotidian ritual, a centuries old tradition, and a centering of one’s soul. The beautifully funky little shed behind Daniel’s house isn’t just a man shack, it is his identity. My role in helping was more midwife than carpenter, the honor of sharing the first sauna more like best man.
So it goes in the sauna building business, I don’t just make little buildings for people, I help them hold onto their identity, their heritage, and their dreams. It’s an honor and a privilege—and always a joy to share that special excitement of the first heating.
Podunk aficionados will recognize this bell that used to hang by the old sauna. Traditionally, the bell was used to alert bathers that a round was over or that the sauna was hot or that someone was approaching from the outside world.
The electric heater, although a far cry from wood, can still give off a nice glow. If installed correctly, it will provide plenty of heat and good löyly.
The inside as it should be: simple and dimly lit. The heat should be felt and almost seen as a shimmering veil that falls over the stress of daily life. Detailing here is clean and rustic, newly built but as old as the tradition of sauna.
My latest project came about because of the enthusiastic insistence of the client, who, with typical Finnish ingenuity, decided that her tiny “garden shed” needed to become a sweet little sauna. Typically, for the electric saunas I build, I carve out space in the recesses of a dark basement or some other unused corner of the house. This space had its own bright little shell for me to work with, perfectly placed a few paces from the kitchen door. The exterior had charm, so I left that alone except for the new galvanized metal roof, which mirrors its surroundings. It is clandestinely tucked into the yard, so that unbeknownst to the neighbors, there is a whole world of warmth inside.
It immediately reminded me of a Tardis. For those of you not up on Dr. Who, of the popular British TV series, a Tardis is a time machine in the form of a phone booth. And Tardis is an acronym for Time and Relative Dimensions in Space. When the door is opened, an enormous interior is revealed. My challenge was to make this 64 sq. ft. shed completely functional as a sauna and feel larger than it is. So far it has surpassed my expectations. It feels roomy, airy, and comfortable for two or three people with a heat that burns deep and a löyly that lingers just long enough. I even fit in a foyer/disrobing area. Stepping out of it in a cloud of steam, it is hard to reconcile the size of the outside with the comfort of the interior.
Like the Tardis, the sauna is a time machine. Once inside, the heat takes you to another dimension as minutes turn to hours and worries melt away like the face on a Dali watch. Sometimes, I want to thank my clients more than they thank me, for the inspiration to create something so perfect and for taking me out of my world and into theirs.
My family name, Licht, came from my German ancestors who made candles—the family crest features a candle—so it’s no wonder that I think about lighting a lot.
The most important thing about building a sauna is creating the right atmosphere. It’s not just about temperature, it’s about engaging all of the senses in a soothing way. The sauna is a sweat bath, light therapy, aroma therapy, and talk therapy session all rolled into one.
With that in mind, I think hard about the quality of the light in the sauna room.
Although all sorts of colored LED and optic fiber lights are available, I try to avoid any electric lighting. In fact, if it is a traditional woodburning unit, I avoid electricity entirely. Not only is it not needed to run a woodburning sauna, but if there is an electric line to the building then there will be a temptation to add outlets and harsh outdoor lighting. The next thing you know, someone is plugging in some beeping device or the light is blotting out the night sky and the whole experience is compromised. What you want is dim light that will let your eyes adjust to the darkness and that will make even the most modest bather feel comfortable, even if their towel happens to slip off. A few candles can be just enough to light the sauna room. The problem with candles is that they will melt in the sauna—even if you don’t light them! To solve this, I install a candle window above the mantle so the candle (or lantern) stays in the dressing room and lights both rooms.
I also consider daylighting and place windows to allow for natural light without compromising a sense of privacy. When rough framing the windows, I leave space so that the window placement can be adjusted to frame the perfect view when seated on the bench (but not the perfect view from outside).
In an electric sauna, I will often put a light under the bench, with a dimmer, so that there is no harsh light, only a soft glow that sweeps across the floor. No one wants to stare at a glowing light fixture (which is exactly the situation in most commercial units). Whatever the situation, I work with the light to create just the right ambiance.
Just beyond the reaches of the village of Trumansburg is the settlement of Podunk. When I was growing up, it was home to some thirty people and a cross-country ski shop. The place was run by Osmo Heila, a Finn, who also sold steam juicers and sauna stoves. Ozzie was an ambassador for all things Finnish. There was a rustic ski lodge, a modest circuit of trails, and a sauna. I was good friends with the family and spent winters there skiing the trails and summers taking saunas and hanging out by the creek.
The original owner of the property, Wilho “Willie” Uitti, was also Finnish, and following tradition, he built the sauna before the house. It was constructed with locally cut wood and with a modest profile. Despite a few upgrades over the years, it maintained a typical Finnish pragmatic aesthetic. New parts were eschewed in favor of jerry-rigged repairs, like the paint can that became part of the stove-pipe. There were a few feminine touches, like curtains in the dressing room, but the sauna room contained only the bare essentials: stove (or kiuas) with its pile of rocks, a water tank heated by the stove, simple benches, and buckets, brushes, and loofas for washing. A window, propped open with a stick, provided ventilation. The spalled concrete floor had a drain and wooden slats, called duck boards, to walk on. The pine wall boards had resinous knots that oozed sap into shapes that made us think of strange creatures, like a speeding weasel. Returning to Podunk in the years after high school, it always seemed the same. The same mementos were in the dressing room, the same plastic buckets were on the benches, and the creatures on the wall had barely moved. But, like the creek meandering behind the sauna, the sauna was slowly changing: being swallowed by the bushes, sinking into the earth, and eroding away.
Taking a sauna consisted of several sessions of heating up, each followed by a cooling down or a plunge into the creek, and lastly, a scrub and a rinse in the sauna room. Afterwards, we relaxed in the house and shared food and drink. Eventually, somebody looked at a clock and we suddenly became aware of the hours that had passed. We called this lost sense of time sauna time.
Applied to everyday life, sauna time means slowing down, stepping away from technology, and observing the subtle changes. It is an appreciation of all that is impermanent. The continuity of life doesn’t come from holding onto things, but from the rituals, traditions, and relationships that one carries in their heart. As the sauna at Podunk slowly degrades into a pile of boards, I am reminded that sauna is much more than just a building and that building saunas is about much more than just carpentry.
Here you can read about my musings on the sauna experience and the sauna design and building process. Some of the information will be practical, some will be wispy and esoteric like the steam of the löyly rising from the hot rocks. Happy sauna-ing!
The one thing that always comes up when people ask me questions about building saunas is “How do you insulate it?”. Intuitively, one might think that the sauna, with it’s high temperatures, would need more insulation than a house and should be as tight as possible to conserve energy. In fact, I’ve had building inspectors give me a confused list of requirements using such logic. The reality is that a sauna is such a different beast than a living space that most energy efficiency related calculations have to be thrown out the window. R-value, the number printed on most insulation products, is the resistance to heat flow of a given material of a given thickness for a given temperature difference (delta T) between the hot and cold side of the material. Typically, in our region, delta T is assumed to be 35° F, but in a sauna, the delta T might be 165°! So, in terms of heat loss, we get some very different calculations. To really understand R-value, you need to think in terms of it’s inverse: the U-value, or coefficient of heat transmission. U-value is expressed in units of Btu/hr/sq. ft./°F, or, plainly, how much heat is lost per square foot for every 1° temperature difference. A typical sauna, with R-13 average insulation, might lose 4000 Btus per hour (or 1200 watts). But, a typical sauna stove generates 25-40,000 Btus of heat per hour, so losing 4000 Btus is not a big deal. (It is more important if you use an electric heater: an 8 kw unit can only put out about 20,000 Btus an hour.) The other factor to consider is that, unlike a living space, you are not trying to hold the heat for very long. So, you don’t need to stack up piles of insulation in the walls and ceiling. In fact, many old saunas had no insulation at all.
Recently, I was called upon by a couple who had bought a property with an existing sauna that needed some professional help. The structure was a cordwood affair: a building method where timber-framed walls are in-filled with short logs, stacked like firewood, with mortar between them. It looked like it came right out of the pages of Rob Roy’s classic how-to book: The Sauna. The exterior was fairly solid and quaint in a hobbit kind of way, but the interior, in terms of functionality, had some serious flaws. The timber frame and log and mortar walls looked pretty good, but it was obvious that the project is a classic DIY affair: a case of a homeowner taking on a project that looks easy but with complex details that get skipped due to a lack of knowledge, funds, or basic skill.
