Combustion air upgrade, wood-fired sauna

I want to share an innovation I came up with that provides fresh combustion air to the wood stove of my sauna. I use clothes dryer ducting to do this. It's relatively simple but it makes for huge improvement in the overall efficiency of the heater. I don't remember how I came up with this. Not that there's much to it but I'd like to think it was an original idea. Maybe it was but usually these sort of things come from elsewhere and I just don't remember.

I was forced to recently refurbish the air intake. Doing so inspired me to write about it so I could share it with fellow sauna enthusiasts. 

What we see here are the remnants of the old clothes dryer aluminum ducting that I used as the fresh air ducting. There's maybe something related to the heat and/or the caustic chemistry of wood ash that caused the aluminum to lose it's malleability. The aluminum skin became wispy and started to crack and fall apart. It lasted about 15 years but now needed to be replaced.

First, some basic wood-fired sauna theory: There are two ways you can situate a wood burning stove for a sauna. One has the feed door on the outside of the sauna space. This might be completely outside or in the antechamber/changing room. The wood stove goes through a wall. The advantage of this is that it keeps smoke outside the sweat space and none of the heat generated by the wood stove is wasted by the fire pulling it into the stove.

There are disadvantages to this though. For one it's a little more of a hassle to manage the burn of the fire since you have to go outside to feed or check on the fire. Second, the wall needs to be built with some consideration so the heat of the stove doesn't, ahem, burn everything down. This is usually pretty straightforward and done with sheet metal or masonry. Third--and which to me is a deal breaker--is that you do not get the primordial, soul nurturing of seeing and listening to the fire from inside the hot dark sauna space.

The other more common method is to have the stove entirely inside the sauna. One of the big draw backs of doing this is that the fire and the "chimney effect" of the fire and stovepipe draw a lot of air out of the sauna space. Also if the fire is dampered, or somehow the chimney becomes blocked, smoke can get in the sauna space. Even worse, in some rare circumstances poisonous carbon monoxide can fill the sauna space. 

Wood stoves consume a lot of air. I remember on certain particularly cold nights growing up in Alaska watching a thick cloud of "fog" roll in from the door and snake it's way along the floor into the firebox of the wood stove. It was eerie and mesmerizing. Sometimes it would be a layer 18 inches or so thick. It would completely obscure the floor. This experience gave me a strong visual impression of the enormous volume of air that gets pulled though the sauna into the stove to feed a fire. That's a lot of cold air getting pulled in from the outside into what should be a hot space!

When I built my urban wood-fired sauna I had this experience in mind. I improvised a method for getting fresh outside air for the wood stove directly to the fire. This would help improve the efficiency of the wood burner: more heat in the intended space and less of it wasted going up the stove pipe. It also provided some assurance that we had fresh air to breathe.

What I came up with is simple and it works surprisingly well. Essentially it is a simple flexible aluminum clothes dryer duct routed so that it terminates right in front of the wood stove door. 

Let the photos demonstrate:

Here's the vent on the outside. (Forgive the un-aesthetic T1-11 and plastic vent cover. No one ever sees this wall!) There were louvers on the vent cover which I broke off. The louvers were there to help prevent cold air from being drawn toward the interior. Nope. We want that! The grill stays on to keep the critters out.

This photo is taken under a bench near the wood stove. The wood stove is to the right just on the opposite side to the cementitious tile backer board. In the recent refurbishment, I replaced both the vent cover and the aluminum wall ducting. Here (above) is the new vent coming in through the exterior wall on the left. The new ducting is pushed through the backer board on the right.

Why is it always so damn hard to slip the ducting on over the vent pipes!

A cementitious cider block is placed near the ducting to protect it from being crushed by fire wood which will soon be piled back under the bench.

This photo shows the ducting going through the backer board (on the left), through another cinder block and terminating right near the door to the wood stove.

It may not be pretty but it works great! My sauna uses an old 1970s-era home heating wood stove. It's welded plated steel so it could potentially handle drilling and welding an air intake but with my method, I didn't have to do this. The ducting was quick, inexpensive and very effective.

For a variety of reasons, I typically do not damper the stove. In fact I often leave the door cracked open just a little to help concentrate the air movement into the stove. This acts like a black smith's air bellows, blowing air onto the fire to really feed it. I want the fire to burn fast and hot. I'm not trying to keep the fire burning over night and since this is an urban sauna I want to minimize bothering my neighbors with smoke. Also a hot oxygen-rich fire reduces the impact on the overall regional air quality--something I care about.

Even though the entry door to the sauna is not particularly air tight, there's still enough negative air pressure for gobs of air to get pulled into the fire directly through the air duct. I know this because when the fire is going well I can put my hand in front of the duct and feel the rush of cool oxygen-rich air being drawn through the duct directly into the stove. The flow is similar to lightly blowing on your hand from about 8 inches away. It's really noticeable!

In summary, while my system is super rudimentary it is an important feature and it works great. In my experience, I believe some sort of provision for a combustion air intake should be made for all wood-fired saunas where the stove is on the inside. It does a lot to improve the heating efficiency and it helps keep the occupants safe.

 Happiness is a sauna with wood under the benches.

My Varusteleka haul

I recently discovered the weird and wonderful Finnish military surplus store, Varusteleka. I've always had a soft spot for surplus. Wool is a great fabric and practical utilitarian clothing tends to be my style. The site often has pretty darn funny, self-effacing descriptions of certain items. (Take for example these now-sold-out Russian army surplus boots.) Plus being in Europe, they have access to more exotic items, particularly former East Block stuff. There's a brick and mortar store in Helsinki but they currently offer $10 flat-rate shipping to the U.S. This makes it hard to resist making orders even for clothing where the fit might be questionable.

Related to this blog, I was surprised to find a couple really useful items for my sauna/bathing/swimming enthusiasm. Here's what I scored:

Towels! 
These are almost certainly from the former socialist republic of Czechoslovakia. Being small they were definitely intended as institutional/military towels. They were designed to get men dried with industrial efficiency. One towel is just large enough to dry someone off. While a few in the batch I got are sort of a dimpled textured cotton, none are terry cloth. For some this may be a no-go. Most Americans these days take for granted a flat piece of fabric is not a towel. (Those who feel this way have not discovered the wonderful Turkish towel tradition of the peshtemal, but more on that later.) 

For me, however, this is exactly what makes them great: The small size means that they work well for fitting in travel bags. I can pack two if I go out to a friend's sauna or, when visiting a public sauna, I can save a few dollars on the towel fee. I always keep one in my shoulder bag now for impromptu swimming in the Willamette River or laps at the local community pool. Since they are not terry cloth, they air dry more quickly and therefore tend to not get as smelly. They all come with a little loop so I can hang them up at work for on-the-go drying.

Why else do I love these towels? A few of them are cotton. But most seem to be a linen blend. This makes them softer and more absorbent. A few I absolutely treasure, as they are almost certainly 100% linen. They have a subtle sheen that is similar to my fancy vintage estate sale dinner napkins. They are silky smooth on the skin. Deelish!!!

It took about two and a half weeks for the box to arrive from Finland. Opening it up, I encountered a mysterious and compelling bouquet. Partly it was that characteristic military surplus odor. (What is that anyway? Rotting rubber?) This was mingled with a cloying but exotic Third-World-ish floral detergent fragrance. Bleech!!! I had to wash them all. Unfortunately, this messed up how they had arrived perfectly laundered and pressed. Since many of the towels are linen (or have a high linen content) they needed to be ironed. It's a huge time suck but I get an odd relaxing satisfaction with ironing these. (Maybe, if I keep buying them, I'll have to invest in an industrial pressing mangle?)

I ordered a fair number, all told I have somewhere around 50 now. Am I out of control? My intention is for them to live at the family cabin in Alaska. They can be used for the sauna there. The towels' inherent efficiency will work well for this purpose: They won't take up too much space. I can store a number of them in case we have guests and they will be easy to wash and identify as designated "sauna" towels. There will be enough so some can stay in rotation even while dirty ones are in Anchorage getting laundered.

Don't hate me! I may have bought them all out. There is however this Hungarian version still in stock--another small towel with hanging loop. They're just maybe not linen but still great!

Sandals!
One difficult lesson I've learned with "sauna-ing" in Alaska is that you really need proper footwear when standing outside in the snow. For my Dad's urban Anchorage sauna, to cool off we usually run around in the back alley. It's relatively private and/or it's fun to, on rare occasions, alarm the new neighbors or tourists with nudity. There's a vacant lot to roll in the snow and the alley is a good place to move around and air out as you cool off, getting the core temperature down for the next sauna hot cycle.

Over the years I've toughened myself up (or gotten used to) dunking in extremely cold water or giving myself snow baths. In fact I love this and saunas just don't feel as good without it. But the one thing I can't get used to is having my bare feet freeze while standing on ice or snow. Oddly enough, it's ok to be completely naked in even subzero temperatures but with bare feet on ice, it doesn't take long for them to hurt really badly even if it's comparatively warm out.

photo credit: Varusteleka.com

Whenever I visit Alaska somehow I never seem to have the right footwear for the sauna. I've often settled for awkwardly slipping into a pair of Sorel boots or lace-up shoes just so I have something to wear in the snow. Then I found these sandals at Varustelka. Sure I could pick up some dollar store flip-flops or maybe some no-name Crocs but these are just too cool! Being army fatigue green, my feet will be camouflaged if shit gets real. The Russian star and Cyrillic writing on the sole adds proper pro-level banya street cred to my sweat bathing. I've ordered enough to have a small sandal army for the saunas in Anchorage and at the cabin. No more frozen feet and we will be bathing in style! Plus they fit great: They're easy to slip on and off and they stay on my feet comfortably.  

I can imagine lots of Finns buying these for just the same purpose. I bet they are popular so the site seems to restock them in small quantities so they don't all sell out at once. Good luck grabbing some.

Plenty of lemons for lemonade in my sauna life

Neighborhood gentrification continues full kilter here in Portland, Oregon and it only seems to be picking up speed. The character of the neighborhood has changed. Off street parking has dried up--and along with it comes the incessant chirping and staccato honks of people locking their cars with their remotes. (Why, people?! Why?! It doesn't make you safer. It's just annoying.) 

The casualties mount: One of my favorite local groceries, Mercado Don Poncho, was pushed out for more up-scale retail. The Know, a cool pretty authentic punk venue will be leaving soon. Both places will probably be replaced by shoe stores or some such. Neighbors I know and care about have become financially stressed and/or are disenchanted and are moving on. 

One new characteristic of this growth is that there has been an uptick in new home construction. Older houses are getting torn down, replaced with bigger or multiple homes. Lots with big yards are being divided and long-vacant lots are being developed. We've heard a lot of hammering lately.

For me there has been one small recompense: free wood! I've been trolling the neighborhood with my pull wagon, bicycle (with bike buckets) and truck, scavenging scrap wood from the construction sites. Much I've burned in the sauna already but I do also have the beginnings of a proper wood pile.

Behold!

Many of these lumber pieces are 2X6s. The building code requires them for exterior walls. Maybe the ceiling of the second floors are a little shorter now or they had to use 10 footers? I'm not sure but there were a lot of short perfectly-cut-for-my-stove 18 inches 2X6s. Heaven! 

My new rule this summer for rooting through the scrap wood piles: pick up nothing that I have to cut--only short pieces. Skip the tiny scraps too. There's such an abundance of wood, why make work for myself? The vertical pieces in the foreground are me failing with this rule. Discipline, Dave! Discipline.

I love burning lumber. Yes, it lacks the concentrated BTUs of hardwood but fir and hemlock burns fast and hot which I think works best in an undampered sauna stove. Plus cut lumber stacks densely--Tetris style!

Urban Adventure Bathing: the Portland Hilton

Did you know that Portland's downtown Hilton Hotel has a spa and fitness facility and that it's open to the public? Yes, there's a fitness room, but all Tinygogo cares about is the indoor pool, hot tub, sauna and steam room. Somehow I managed to work downtown for almost seven years before learning about it.

For $20 a visitor can drop in for full access to the facilities.This is conservative corporate America, so bring a swim suit. It's required. (I managed to not get kicked out after prancing around in my speedo.) The important thing is that this is a relatively unknown location where you can sneak a sensual escape from the troubled world.

Lockable wood lockers (at least in the men's area)

Here are numerous private showers. Be careful you don't give yourself a seizure from the black and white checkered tile. The Dream Police, they're coming for you.

This is the entrance to the sauna. It's perfectly serviceable, hot, good benches and large. Nothing fancy but no complaints either. It didn't have a bucket for steam but I improvised by filling up a few paper cups of drinking water.

And this is the entrance to the steam room. I thought it was well-designed and maintained. Too often steam rooms are a token addition, where tile might be missing, or it's luke warm and clammy (and even moldy). There were two levels of tile benches and the ceiling was an upside-down pyramid design, so condensation on the ceiling was channeled to a central spot in the room. It didn't drip on me and it was fun to watch.

The negative with both the sauna and the steam room was that there were no nearby showers for cold rinsing. It felt a little awkward to walk through a carpeted hallway and through the changing room to get to the showers. 

The swimming pool was certainly not Olympic length but you can still do some laps to get the blood moving. It works as a cooling plunge pool too!

Ah, the light! The roof above the swimming pool is a nice treat. I floated on my back and stared at the sky.Good bye, stress.

Hot tub! It's a stainless steel tub, which is a nice step up from nasty acrylic. (The black and white checker board theme returns to haunt me.)

Honestly I didn't fully relax on my first visit. As a non-hotel guest and as a ruthless blogger I felt like a bit of an interloper. Also the environment is a little sterile. But, in the spirit of Urban Adventure Bathing, I resolve to overcome these obstacles and make this place my own. I am keeping this place in my secret emergency reserve if I ever have to escape for an inappropriately-long lunch hour from a tough day at work. 

Urban Adventure Bathing

Here Tinygogo introduces a new column: Urban Adventure Bathing.

It's a war out there. We live in an unnatural environment doing unnatural things: computers, cars, fast food, fashion. Sometimes it's all too much. I can't change the world but I can fight back in my own way. I may be stuck in a stressful full-time job but I can still sometimes escape and find respite by way of a relaxing sweat and/or soak. Bathing is my way of getting out of my head and reconnecting with my senses. I've learned that it's an important, fundamental aspect of having a quality meaningful life. 

There was once a soak and sauna facility that referred to itself as an "inner-city hot springs." It's a nice sentiment and there are certainly wonderful places like this that Tinygogo will share with this column. Others are more challenging. I say explore them all: the odd, bad and wonderful. Let's make it an adventure. 

Wake up body! Radical sensuality reappropriates our spirits from the artificially-sweetened media noise that is constantly attempting to possess us. Viva la revolution en paz. 

With Urban Adventure Bathing, Tinygogo plans to embark on a journey of discovery. Where can we go to have a good sauna, soak or steam? It's pretty rare that I can escape to an isolated natural hot springs or backwoods sauna. I have to make do with what I have here (mostly in Portland, Oregon). We can still find sensual escape within our concrete jungles. There are many options out there and this column will share them.