A Modest Affair
Finishing a job is always a sweet endeavor. I usually budget in one day of fussiness: A day when I can pay attention to all of the little details, get the stove in place, and then, as a last step, give the sauna a test run. This is when I get to see how my efforts have paid off and take note of how the sauna actually fires. Is it hot enough? Is it light and airy and does it have that right sauna feng shui? Does it reach a good temperature and would Ozzie—the Finn who started me on my sauna-building path—approve?
The job I just finished is a modest affair: bare bones, applying that Finnish sort of pragmatism. I converted a kit-built garden shed, the type you’ll find lined-up on the edge of a big-box home store parking lot, into a simple sauna with no dressing room. I liked the challenge of working within a modest budget, and I liked the folks: down-to-earth, modern-day Helen and Scott Nearing types. I had to remind myself that a sauna does not have to be a luxury item, affordable only by those in the higher income brackets. A sauna should be as essential and ubiquitous as indoor plumbing.
I lined the inside with knotty pine—a low budget alternative to cedar. Sitting on the top bench, I noted that the smell of pine reminds me of my forays into woods here in the east. It is a familiar smell, close to my heart, unlike the rarefied smell of cedar. Aside from the knots, which will forever bleed sap that will inevitably find it’s way into someone’s hair, it is a fine wood to use. It is not as stable as cedar, but the inevitable cracks will open the sauna up and let it breathe. We always said that Ozzie’s old sauna at Podunk, with its gappy, knotty-pine walls and sagging ceiling, felt better than any other.
My Lämpimämpi stove fired fast and hot. The rocks quickly reached good löyly temperature and the first splash of water had me moaning in ecstasy. At no point did I feel that claustrophobic locker-room-sauna feeling of not being able to breathe. The dual windows filled the space with light. The benches will hold the couple, their kids and several neighbors. In term of essentials, it is a perfect sauna. Nothing more is needed—no fancy tile or trim work, no designer dressing room. It works, plain and simple, and it works well. It was the best sweat I’d had in a while, and a good sweat is almost payment enough.
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.
