Wood-fired mobile sauna by Rob Licht Custom Saunas.
Although Glamping is a term that was coined in the early 2000s, the concept of an adventure in nature bolstered by all of the modern conveniences one could muster, or have mustered for them, has been around for well over a century and a half. In 1869, writer William H.H. Murray of Boston extolled on the virtues of experiencing the Adirondack backwoods in his book Adventures in the Wilderness. This inspired an avalanche of urban neophytes flocking to the woods in search of adventure and to commune with nature. These adventure seekers were known as “Murray’s fools.”
People traveled great distances and endured great hardships, such as days of travel over log roads (which were literally made of logs placed side by side) to get to the heart of the Adirondacks. Once they arrived, they sought out the services of guides, who did everything for them—transporting them in their guide boats, making camp, catching and cooking their meals. In essence, these early Glampers brought with them from the city every expectation of service they would get at the finest hotel.
“The mountains call you, and the vales: The woods, the streams, and each ambrosial breeze that fans the ever-undulating sky.”
—Armstrong, Art of Preserving Health
Glamping experience enhanced with a sauna (banya) in tow.
While part of me chuckles at the concept of Glamping with it’s pretense of tender-footedness, part of me is drawn to the concept of rustic luxury. Although I am as far from a camping neophyte as one can be, with years of deep woods experience and many a night sleeping on hard ground, the concept of luxury camping does have a certain appeal to me now. I’ll sleep in a tent on a platform—with lights and heat and maybe a commode. But better yet, with a sauna next to it.
The idea of communing with nature combined with sauna is perfection—and something, I bet, even the luckiest of Murray’s fools never had.
View of the mobile sauna looking out through the dressing room to the campsite. Pile of rocks sit on the Lämpimämpi stove.
Recently, I posted a picture of our sauna fire burning hot and mentioned Sam McGee. For those who don’t know, Sam McGee was the sad character from Tennessee who could not take the cold of the Yukon in the poem The Cremation of Sam McGee by Robert Service. His last wish was to be cremated, a task his friend dutifully tried to complete. The ending had the narrator peeking into the make-do crematorium in the boiler of the derelict ship stuck in the ice on Lake Lebarge. There was his late friend Sam McGee, as warm as could be, calling out for him to shut the door.
Whenever it is extremely cold out, as it has been recently, I think of this poem and the warming power of a hot fire. I love it when the mercury dips below zero. There is something invigorating about having your snot freeze when you breath hard or having sweat icicles dangling off of your brow. I love cross-country skiing in the dark, in the cold, when two hats and two pairs of gloves are needed. One false move, and the night might end like in the story “To Build a Fire” by Jack London. Another favorite read from Middle school when I dreamt of all the great explorers who ventured into frozen lands.
Walking through the snow towards a hot sauna fire.
I remember my senior year of high school, the year Cayuga Lake last froze over. That was a cold winter. We did a lot of cross-country ski races that season. With our skimpy race suits and lowtop boots, we had no protection other than the fire in our hearts to keep us from freezing to death. During the Canadian Ski Marathon that year it was minus 40° at the 8 a.m. start. Celsius and Fahrenheit. If you blinked too long, your eyes would literally freeze shut. Grandma volunteers would slap our cheeks at checkpoints to make sure we didn’t have frostbite (and we still wore our skimpy suits). By the end of that year, my parents had moved to the heart of the lower Adirondacks. The Black River valley, where our house was located, was often the coldest spot in the lower forty-eight. It was minus 25° F for days on end. Thunder boomed from the river each night as the ice expanded. The ice was several feet thick; I have no idea how the fish survived. I loved to be out in that hostile world: skating, skiing, or snowshoeing. It was the cold of a Jack London story. Your spit would freeze in mid air and hit the ground with a crackle.
During that cold winter in high school, I had a hot sauna to crawl into after our ski races. But not in the years after. When I moved back to the Finger Lakes after college, I went back to that sauna at Podunk, weekly, until I could build my own. I have kept up the ritual ever since. On these freezing nights it is never too cold for a sauna; in fact, I relish those times when one can experience the 200° (or more) difference, going from the hot room to the night air. Your feet freeze to the ground and your hair sports punk icicles.
There’s no need to wait until you are cremated to be truly warm. Poor Sam McGee, if only he had a sauna!.
Lately, I have been thinking about the application of the foil I use in my saunas as a radiant vapor barrier. Perhaps this is because it is almost Christmas, and I was thinking of how my family decorated the tree each year. The final touch would be to drape foil tinsel over everything; our mother would have to constantly damp down our enthusiasm by reminding us to place it carefully on each branch, not to throw it.
This suspicious sauna foil is aluminum-coated plastic—upper working temperature of only 131-248° F (55-120° C). This product compares to the ubiquitous foil “bubblewrap” people and is not to be used inside your sauna walls.
There are tricks to using radiant vapor barrier foil, but the first and most important step is to buy the right stuff. Like the tinsel we put on the tree, the foil may actually be aluminum-coated plastic—which you don’t want to use. That plastic is likely polyethylene, which, if you look it up on the material specification sheet that every product has, has an upper working temperature of 131-248° F (55-120° C), meaning it will likely melt at typical sauna temps. Sauna Foil, available from any of the familiar sauna suppliers, is aluminum foil on a kraft paper backing. I used to find it with fiberglass reinforcing thread, which is helpful because the stuff tears easily. Four foot rolls, rather than three foot are helpful so you can do a wall in two passes, but I have trouble finding that width.
I recently tried a new supplier selling four foot rolls of sauna foil, but upon opening, it had a suspicious plastic look to it. That night, I put it in the sauna and within seconds it began to distort and curl up like the polyethylene I suspected it was made of. (see illustration above)
The second trick is to design the wall correctly. I read and see a lot of misinformation that touts using no air gap with foil. This is wrong. The air gap is essential. The foil works by reflecting radiant heat. All black bodies1 give off and absorb radiant heat that travels in a straight line from one hotter object to another cooler one; the hotter the body, the more heat it emits. The sauna rocks radiate a soft heat to you, the walls, and the benches, and that is why you want the sauna to be laid out so that everyone has a view of the rocks. The fire, if seen through a clear glass door, also radiates heat but at a higher intensity—too high for a comfortable sauna (but great for ambiance). With an air gap of at least a half inch, when the heat hits foil, it is reflected back into the room or the backside of the cedar. Because the foil is also a perfect conductor, if it touches the back side of the cedar (as will happen with no air gap), it pulls heat away from the cedar and transfers it to the wall space behind the foil air gap.
Air gap. A sauna building best practice.
I’ve understood this thermodynamic principle for a long time. I took a class called Solar Design and the Energy Efficient Home in my first semester of college. We learned all about insulation, heat transfer, and basic building skills. The first day of lab, wherein we built a timber frame house, I was handed a Makita 12” circular saw. My building career started right then and there.
With the web of misinformation out there, I had to think of a way to illustrate this basic principle of thermodynamics. So, one slow day in the shop, I rigged up an experiment and photographed it (see illustration below). I set up a section of cedar wall about 18″ from my infrared shop heater and fastened two pieces of foil to the back, one with a 3/4″ air gap, and one with no gap. After an hour the cedar was 250° F on the front—like it often is in my sauna. The back of the cedar was 121° F, which is impressive by itself. The back of the foil with no gap was 115° F, meaning it was acting as a perfect conductor, and the back of the foil with an air gap was 71° F: room temp. The air gap was clearly making a difference, 45° in this case.
The thermodynamic experiment begins.after an hour on cedar.back of cedar.back of foil, no gap.air gap makes a big difference!
The foil is a perfect vapor barrier, rated at zero perms—meaning no vapor moves through it. But unless you layer it properly, with insulation behind it, the moisture will condense on it or the first cold surface it hits. Even in a perfect build, there might be cold spots in the insulation (typically about the size of a mouse hole), so there likely will be some condensation, but this is not a problem if there is air movement. The air gap behind the cedar allows air to circulate around the cedar, removing any moisture, and ensuring that the wood heats and dries evenly and remains stable. Heating one side of a board and wetting or cooling the other is how you make curved boat staves.
There are other tricks to using the foil: unrolling it and rerolling it foil-in, using temporary magnets when working a commercial job with metal studs. But the key is to use care. Use plenty of hi-temp foil tape and patch tears as you go and work with a partner if possible.
I suppose you could build a sauna by putting a heater in a refrigerator box, but that would last about a day and be incredibly wasteful. Cedar touching foil won’t ruin your sauna and neither will plastic melting in the walls where you don’t see it. But if you are going to take the time and bear the expense of building a sauna, you might as well do it and so it will last generations. I guess my mother was right: applying foil carefully and not just throwing it up is the way to work.
You’ve probably heard that I’ve spent a lot of time in and around the saunas. But another hot spot I’ve spent a lot of time around is kilns. Specifically, foundry kilns and ceramic kilns. Unsurprisingly, there is a strong relationship between the two, as they both involve getting things hot. In the lost wax casting process, investment or ceramic shell molds are heated to roughly 1500° F. The extreme heat burns off the wax original, and thus, the lost wax of lost wax casting. This can take hours or even days depending on the mold type and size. A ceramic kiln can get much hotter, up to 3000° F. That is hot enough to melt steel and many other metals.
I learned how to do bronze casting in art school. It is an ancient process, and my classmates and I did it pretty much the same way that it was done thousands of years ago. We learned to determine how hot things were by using our senses. All objects emit radiation when heated but at about 1100-1300° radiation becomes visible. Peering into a hot kiln (safety glasses strongly suggested) is like looking at another world, perhaps on some gaseous alien planet. The blast of heat through the spy-hole is like a ray gun. Solid objects become transparent. Heat and light become one; the heated molds don’t reflect light but emit light. We rarely used pyrometers (hi-temp thermometers), and when we did, it was only to affirm what our senses were telling us. We recorded the smells of things burning off. When the smells were gone, the molds were clean and ready to accept the molten bronze.
When a kiln is loaded, there is always discussion about the hot spots—certain delicate molds need to avoid the highest heat while larger molds might need it more. There is always conjecture about how the heat circulates; a whole aspect of kiln building is dedicated to controlling the flow of heat within the kiln. Some of this conjecture is borne out in the results of a firing—whether things fire correctly or not. Ceramicists use cones: small tapering forms that bend at specific temperatures. After a firing, these devices will give a true telling of how the firing went. But despite the science, there is still a lot of mystery and art to the process, so much so that a firing of a large kiln can take on a ritualistic feeling. Staying up late to tend the kiln (as is done with wood fired and other non automated kilns), drinking beer, and heating up pizza on its surface add to the aura.
Thinking of all of this casting lore makes me think of sauna. Both processes have been done pretty much the same way for millennia, involving community and an aura of ritual. Both focus on fire and heat, and even as well studied and commonly practiced as they both are, there is still a bit of mystery involved in each process.
A kiln is like a sauna on steroids. The heat is so amplified that its flow and effects are unmistakable. Observing a kiln is a lesson in thermodynamics. In the sauna building culture, there is a lot of banter about how to best heat, insulate, and vent a sauna. Yet, all of it is conjecture, based on theory, until one sits in a sauna and feels the heat radiating off the rocks and the wave of löyly hitting the sensitive tips of your ears.
When I design a sauna, I draw from my years of kiln experience. I think of the heat as a visceral substance, almost visible, as in a kiln. I relish using my senses to discern quality rather than depending on technology. Even if the sauna is electric with a digital control panel, I rely on feeling, not the number on the display. I imagine the flow of heat like the way it flows in a kiln. My foundry experience has informed my understanding of sauna in ways that are hard to describe, but suffice it to say that I have always been drawn to fire and to the mysteries that it holds.
Candle windows hark back to my time at Podunk, where the light in the sauna came from a bare bulb in a porcelain fixture outside a little square window into the dressing room. A sauna is too hot for a standard light fixture, so this arrangement made sense. Later, after I started building saunas, I learned that this was a more modern incarnation of the original candle window, which was literally a window into the dressing room with a shelf for a candle to sit on. These windows are common in Finland in freestanding saunas away from the house. The candle window allows a special, spiritual, summoning light into grace the sauna. Especially on those dark winter nights.
In the sauna tradition, we slow down. The flickering candle-light, seen from the bench in the sauna, lures you to relaxation and reflection. Life and relativity. Could there be a more tranquil way to release the stresses of the day?
Although it is this quality of the light that is so important, the candle window is totally pragmatic in a very Finnish way. A candle in the sauna room would melt even if not lit, so this setup was an obvious solution to the problem of lighting the dark interior of the hot room. Despite its pragmatic origins, I find it is also a chance for a little expressive design: it can be round or square, arched or colored. It can have an organic flare to it. Now, with cheap, battery-operated, multi-colored LED lights and even fake candles that look real, the light can be more than a simple bulb on a pull-chain porcelain fixture and be safe. Even if the sauna has built-in electric lighting, the candle window can be a signature element, one that distinguishes a personalized custom sauna from a generic kit.
It’s in the details.
Finnish pragmatic design inspiration comes from using what is available at hand and letting that material influence your design. There are many places to incorporate little details and personal touches: stick hardware towel pegs, stone-faced walls with stones from your backyard, thresholds of locally cut locust, round windows, etc. Think of decorative elements you can hang above the mantle. In my sauna building plans (which can be purchased and download), there is more about windows: framing information and tips on using windows safely in mobile saunas.
Wood-burning sauna with candle window to dressing room.
Here is a collection of the candle window designs and builds I’ve used over the years in and around the Finger Lakes and throughout New York State.
The kiuas, or heater, is the heart of the sauna. In a wood-burner, it is commonly referred to as the sauna stove, but a wood stove it is not! There is a lot of misconception around the kiuas and how it is different from a wood stove that you might use in your house.
First, some history. The modern house stove is really a heating device designed to add comfort to your home while conforming to certain safety and smoke emission rules. Typically they are not used as primary heating appliances, unless you live in a cabin off-grid somewhere. Back in the 70s, during the energy crisis, woodstoves became popular as a way to save money. They were pretty much unregulated and varied in design from a kit that consisted of a door and a flue collar you could slap onto a used fifty-gallon drum, to a more complex Vermont Castings wood stove. Earlier stoves had little control over combustion; these evolved into airtight units that could keep a fire smoldering all night, if not for an entire season. I had one of these highly efficient stoves and didn’t let the fire go out all winter except to clean it. Cleaning the chimneys on these units is an imperative: when wood—especially if it has not been cured for two years—is burned slowly by reducing the combustion air to near nil, creosote forms. This is the result of the wood’s resinous gasses condensing on the inside of the cool chimney walls. As a result of the slow burning, these stoves emit a lot of smoke. After many houses were lost to chimney fires, safety regulations were put into place, and stoves are now required to use catalytic converters to reduce emissions, much like on your car. These regulated stoves require a religious adherence to the use of dry wood, lest your catalytic converter clog up, which they tend to do. Such stoves evolved into today’s models that use a carefully designed system of baffles and airflow to make fires burn efficiently. Now, all wood-burning home heating devices installed in the US must comply with UL (Underwriters Laboratory) safety standards and increasingly stringent EPA standards for particulate emissions. The stoves work well and are very cozy but, by design, they heat up slowly and are not meant to burn all night long not to mention all season long. Because they are intricate designs with interconnected parts, they are all cast iron. The exception is some stoves made in the pre-catalytic converter era, which were welded steel.
So, that is a wood stove. You may find a used one and think you can build a sauna around it, but the truth is, with the rare exception of one of those 70s all welded steel stoves (not the barrel ones!), you can’t. You can build a small hot room with a wood stove, but it will never be a real sauna. Here is why: A sauna stove, or kiuas, is designed to do one thing—heat sauna rocks. It is the hot rocks that heat the sauna and produce bursts of löyly steam, the essence of sauna. Early saunas did not have metal stoves. They did not even have the technology to make a metal stove, all they had was wood, earth, and rocks. The kiuas was essentially a hollowed out pile of rocks that lacked a chimney. A fire was lit within, the room filled with smoke, and after the rocks got hot, the fire was extinguished and the room cleared of smoke via vents and thereafter the rocks heated the room. The closer you can get to that smokey ideal—Savusauna experience—the better.
A sauna stove is not a wood stove; it fires hot and fast, it burns sticks not logs. Its job is to heat rocks. If fired correctly, you will never have to clean the chimney. The appropriate hot fire will combust all of the sticky wood gas and reduce creosote buildup. It is welded steel—can stand up to having water poured over it while red-hot. Cast iron cracks or explodes when subjected to this. It can take the weight of a hundred or more pounds of rocks sitting on top of it when cherry-red. Ferrous metal takes on specific colors when heated. At 1400° F, it is cherry red. At that temperature, an 1/8 inch plate of steel is as malleable as taffy on a hot summer day at the beach. I’ve repaired many sauna stoves with tops that looked like an egg carton from the stones pressing down on the hot metal. So I started making stoves (my Lämpimämpi sauna stove) with 1/2 inch thick plate at the top. I fire my stove so hot that I see dark, cherry-red glow underneath the stones. I swear that sometimes I can read a book by the glow coming off my sauna stove. If you fired your home-heating wood stove like that, you would be crazy. I like to test the limits of my stoves to know they are safe.
When you light a sauna stove, you want to fire it, that is, bring it up to temperature quickly. Use paper and dry kindling and then stuff it full of sticks, not logs (wood scraps from building saunas work great). Because sauna stoves are for intermittent use, they are exempt from the EPA particulate rules. But, the truth is once it gets going after about ten minutes, it should burn so hot that there is no smoke at all. Other than the shimmering light from the escaping heat, I can’t tell if my sauna is heating up by looking at the chimney. House wood stoves are tame devices, meant to be safe. Sauna heaters are another beast. That is why I will never install a wood-burning kiuas in a sauna in the home or attached to a house. Wood-burning saunas do burn down now and then.
If you are building your own wood-burning sauna, you may have a building inspector involved or have to get a wood-burning appliance inspection for your home insurance, and that may require a UL listing. The only heater with a UL label is the Lamppa Kuuma stove. Most others are made for the European or Canadian market, which use different standards. So, before you click on “buy” you should have a conversation with any inspectors involved. They may love the idea of a sauna, or they may think you are crazy to sit in a small hot room and throw water on a red-hot wood stove. In that case, you’ll have to convince the inspector that it’s something that’s been done millions of times without incident. In any case, you will need to make a safe installation of your kiuas. There are clearances and heat shields and floor hearths, none of which can be cheated on, unless you don’t mind owning one of the saunas that burn down. There is also combustion air to consider, which is why I like to fire mine from the outside. The sauna stove sucks up fuel and oxygen, so it’s better to not be sucking the air out of the tiny room you and your friends will be in. This is not such a problem with house wood stoves; although, it is an issue with newer air-tight construction and tiny homes.
So, before you purchase that old wood stove you find on Craigslist, do your research. Think hard about investing in a real sauna stove. The kiuas is not a wood stove. The kiuas is the heart of the sauna.
My stove pipe will get cherry red! After ten minutes, a hot fire should burn clean and smokeless.All stoves will smoke initially.Nothing bigger than your arm!This armload of ash will fire the sauna.Fill the stove and let it burn hot before closing the ash drawer.
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