Wood burning sauna: feed from the outside or inside?

When designing and building an authentic sauna, the question of inside feed or outside feed comes up a lot.

SHORT ANSWER:

I recommend feeding wood burning sauna from inside the hot room.

Reason #1:  heat loss

There will be 25% heat loss from feeding a wood stove from the outside.  This is not my figure, but confirmed by Daryl Lamppa, 3rd generation Finnish sauna stove maker.  The front of the stove is thee hottest.

Reason #2: cost

If building a sauna with feed through a wall, it costs $500-$1,000 more in materials, as code requires metal framing and clearances to non combustibles.   Plus there is the intangible cost of concern to frame a stove inside a wall.

Reason #3: ambiance

A glass window helps create a warm glow vibe, gently dancing off the cedar walls.  Ahhhhhh.  What about the mess from feeding wood from inside the hot room?   No big deal.  Get a hand broom and sweep it out once and awhile.

Hi Glenn,

I discovered your site and appreciate all the information you have here–I discovered that we have a great sauna stove mfg. right here in Minnesota–so that was good to learn.

I’m dreaming of building a wood burning sauna, so I’m looking at floor plans. I see one plan you recommend is to have the stove at the rear wall, centered in the sauna. Does this mean feeding the stove from the outside?

I was in a sauna this fall that had a changing room, and you fed the stove from that room. That seemed like a good idea to me, because the stove was inside…any particular reason for not feeding the stove from the changing room? Maybe it’s better from outside, so you have more room and less mess in the changing area?

Just curious about your thoughts on this as I start my research.

Thanks,

John
St Cloud, MN

Hi John:
Glad you found the site, and glad you find it useful.  it’s nice sharing the joy of sauna.  I particularly enjoy building saunas as you can see.
With regard to feeding a wood burning stove, i am a big fan of feeding from inside the hot room.  In the old days, an outside feed made sense because sauna stoves were not very efficient.  It became a will of sorts, overcoming inefficiency with more logs, stoking the heck out of a barrel stove or home made contraption.
The feed from changing room is a viable option.  It saves a bit of space, and offers heat into changing room.  In my experience, however, this is unnecessary.  Heat gets in the changing room just fine by opening and closing the hot room door.  Further, feeding through a wall requires some elaborate fire proofing and framing around the “throat”.
Today, wood burning sauna stoves are very efficient.  I can start and take a sauna with a handful of firewood tucked under my arm.  Loading from the hot room has never been much of an issue for me.  BONUS:  many wood burning sauna stoves, Kuuma included, offer a glass window.  A wonderful aura, turning the light off in the hot room and seeing a warm glow reflecting off tongue and groove cedar in the sauna.  Magical.
Hope this helps, please stay in touch.
g.

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