“My wood burning sauna takes 3 hours to heat up:” Problem solved!

Unless it’s a savusauna, or John’s Wisconsin sauna, a wood burning sauna shouldn’t take 3 hours to heat up. One of the great things about a wood fired sauna stove is that wood heat can pack quite a punch compared with electric heat. This, of course, assumes that you have invested in a kick ass wood burning sauna stove. Tin can toaster ovens exist in both electric and wood fired sauna stove configurations, of course, but we know better than this. We know not to throw money down the drain by purchasing a sauna heater we can carry with one hand.

So, what happens if we have invested in a kick ass wood burning sauna stove and it takes forever to heat up?

Good news: Here comes the four horsemen for high performing wood burning saunas. Let’s discuss them one by one:

  1. Draw
  2. Ventilation
  3. Insulation
  4. Good wood (that’s what she said)

Draw

A wood burning stove of any type requires good draw. Good draw requires a chimney system that is tight. We light a piece of birch bark or a crumpled piece of newspaper within the firebox, and then the hot air pushes its way up the chimney. In its wake, more air is pulled into the firebox to replace the warmer air going up the chimney. As the flame gets brighter and bigger, the draw increases, more draw and faster.

What can impede this process is a leaky chimney system. Like a vacuum with a hole in the hose, a fire can burn in the fire box but there is no air going up the chimney and no air to come behind to fuel the fire. You need a chimney system that is tight.

Imagine putting a plastic bag in the gap where your wood burning sauna stove connects with your stove pipe. Then imagine going on the roof and pouring water into your chimney, at the top. You’d want water to fill up the chamber. No leaking. That is the hypothetical measure of a tight chimney system and the foundation for good draw.

A second issue is too many bends and twists in your chimney. Here our problem is different in that hot air struggles to work its way through bends and horizontal runs to push its way through the chimney. I am a big fan of chimneys that go straight up from the sauna stove through the hot room ceiling and up through the roof. Yes, 45 degree elbows and chimney through the wall can work. But these systems will require more “oomph” in the form of an extra crumpled piece of newspaper or birch bark or perhaps another form of petroleum persuasion.

Good draw up the stove pipe and up the chimney (no leaks in the vacuum hose)

Ventilation

Ventilation in the hot room is not just critical for a great sauna experience (read: the holy trinity of good sauna: heat, steam, ventilation). Ventilation is critical for burning wood in our sauna stoves. Just as a candle will extinguish if you put a glass over it, a fire in a sauna will want to do the same in a poorly vented sauna hot room.

A fire in a wood burning sauna stove needs lots and lots of oxygen! A shit ton more oxygen than you may think it needs. Why? because in addition to oxygen for fire to burn, bodies on the bench also need lots and lots of oxygen. Just as a candle goes out if you put a glass over it, a fire inside a wood fired sauna stove will putter and sputter if you deprive it of oxygen.

As Wim Hof says: “breathe motherfucker” and this is what we want to do inside our wood burning saunas.

Vents with chutes offer infinite control of the action

Insulation

If living in a temperate wimpy ass climate, you can get by with a wimpy insulated sauna. Barrel saunas, as example, separate themselves from the hot room to outside with a layer of wood. That’s it. And if you are taking a sauna in the foothills of Los Angeles or burrows of Sydney, you may get by with a wimpy insulated sauna. But a good sauna is like a green egg grill. In a well insulated hot room, the BTU’s produced from a wood burning sauna stove efficiently and effectively heats the hot room. Heat from the sauna stove transfers into the stones and mass of the material in the hot room. And we get the deep dense reward of good heat.

And foil vapor barrier is a must.

Simply put: A well insulated sauna heats quickly and thoroughly.

a sauna hot room, with blocking for sauna benches, ready for foil vapor barrier.

Good wood

The fourth horseman to a wood burning sauna is good wood (that’s what she said). It’s obvious to those of us who have learned the hard way, but “dead wood” is as bad as “green wood” in terms of not producing the kind of BTU’s to make our saunas hot.

Dead wood is over seasoned wood. Overly dried out, devoid of gasses wood.

Green wood is wet unseasoned wood.

The best wood is about 20% moisture content. As most of the BTU’s in firewood is from the gasses emitted during combustion, not the material itself, we want to ensure we are burning well seasoned, not over seasoned decent firewood. More on firewood here.

Good wood, haircut sold separately.

If you checkmark these four horseman and your sauna still takes forever to heat up, well, then it’s time to turn your attention to your sauna stove. A kick ass sauna stove is your best investment to good sauna. Good heat makes all the difference. We build our saunas one time and get to enjoy them the rest of our lives.

1 thought on ““My wood burning sauna takes 3 hours to heat up:” Problem solved!”

  1. Thanks Glenn for pointing me towards the Kuuma Stove – it’s a marvel – I light it with one match – an hour later, the sauna is above 200 degrees! – (or cooler if we put in less wood, when we want that).
    It takes minutes to clean and set up each day.
    It produces all the loyly We can handle.
    Adjusting the air intake as it burns is minimal and simple as can be.
    Bravo!

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