Wood burning sauna stove: load from inside or out?

When building a sauna, there are three ways to consider setting up your sauna stove:

  1. Load wood from the outside
  2. Load wood from the changing room
  3. Load wood from inside the hot room

Options #1 and #2 involve using a ”throat” add on to a wood burning sauna stove.  Also, one needs to brick around the throat and sauna, usually a three foot border, for fire retardant.   In the old days, most saunas were built #1, loading wood from the outside.  The main reason for this is that old saunas were inefficient, basically home made iron boxes that burned hot and fast, requiring a pretty much constant supply of firewood.  Finnish ingenuity gave way to the idea that the door to the sauna stove could be steps away from an outdoor wood pile.

As stoves became a bit smaller and somewhat more efficient, people began building wood burning saunas to feed from the changing room.  The theory here is that a small amount of firewood could  be kept dry in the changing room and added to the stove from there.  The main advantage to #2 is that the sauna stove can provide some heat to the changing room.  It is estimated that between 10-15% of a sauna stove’s heat comes from the front of stove.

#3 is my choice.  Today’s sauna stoves are very efficient.  The Kuuma Stove is so efficient that I can take a sauna with 4 pieces of firewood.  By feeding from inside the hot room, I capture 100% of the heat in the hot room, and don’t have to mess around with extensive brick framing.  Also, I can monitor the fire from the sauna bench.

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7 thoughts on “Wood burning sauna stove: load from inside or out?”

  1. It all sounds so wonderful…..except…I need some advice. I too have a log sauna (10×12)with a dressing room that is heated by a through the wall Kuuma stove.

    The problem is the stove burns so dirty that I’m ashamed of using it during the day for fear the neighbors will call the Fire Marshal. Multiple cubic meters of thick smoke belch from the stack.

    I’ve tried everything. I burn dry seasoned pine and ash from the front like Kuuma says (sort of like a cigar). This seems to work for a short while, but when I add more wood to the stove it is impossible to make it ‘burn from the end’. The draft settings don’t seem to make any difference at all. The only thing to do is to open the ash pan door and watch it like a hawk.

    Can anybody tell me what I am doing wrong? The sauna room is about 700 cubic feet (20 CM3) with an R27 ceiling and 6 inch logs.

  2. Bruce:

    You have a unique problem and may need a sight inspection. Where are you located? Please email me separately. I have built and used well over a dozen saunas using the Kuuma, and one of it’s virtues is a clear burn. It vaporizes smoke gases (burning wood gets 60-70% of it’s BTU’s from burning off the smoke) and burns super efficient. A couple possibilities:
    1. Not enough air flow in your changing room… it could be hungry for air, even with your draft open all the way. Try burning the Kuuma with your outside door open for awhile.
    2. Restriction in your chimney,either from elbows or something stuck up in there, or too restrictive of a rain cap.
    3. If all else fails, let me know, i’ll check with Daryl Lammpa..

  3. Hello, thank you for your efforts one teaching people how to build saunas. I am building my own sauna and looking for more detailed information for how to construct the wall area/opening around the throat of the stove for a through wall stove design. In this article you talk about using brick, is this the only way? I am building a mobile sauna so it will be on a trailer subject to vibration which may crack the brick. I have seen mobile Saunas which do not appear to use brick on their through wall stove section, such as in the great book Mobile Sauna compendium https://www.amazon.com/Mobile-Saunas-compendium-modern-nomadic/dp/1467958980

    Perhaps i could use metal flashing and fireboard? If you could point me towards some resources, that would be great, thanks!

  4. Hello,
    I have a quick question. I am also looking at building a sauna with a through wall wood fired heater design. I like the idea of some of the heat heating the adjacent room as a change room. I am also curious about wall separation. I was looking at constructing that wall with steel studs, concrete board and tiled. Would this work or does that wall need to be masonry?

  5. mike: you’re on it. steel studs, concrete board, tile.. i’ve done exactly this. Actually cultured stone. This works!

  6. Glenn,

    Thanks for the reply. One other quick question. What insulation do you use for the sauna walls (also the sauna wall between the stove opening and stove body if using the through wall design). I was thinking Roxul Rockwool which is non combustible. Would you recommend that?

    Sorry one other question that is not related to this thread but hoping you could help out. Would you ever recommend an electric heater for an outside sauna? Do electric heaters generate enough heat for this application?

    Thanks again.

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