Straw/Clay Sauna

Finished straw/clay sauna with post and beam and metal roofing
Finished straw/clay sauna with post and beam and metal roofing

Drawing showing rocket stove heater and urbanite foundation
Drawing showing rocket stove heater and urbanite foundation

“Ok, the Rocket Stove heated, Cob Sauna is on!! There is a client who will pay me to build one, which is GREAT! ‘Cause it means I’ll actually have the time to build it, and see it finished in a timely manner.

I’ve delivered the urbanite for the foundation today, I’ll be prepping the parts and picking out the brick and whatnot tomorrow. Hopefully by Friday, I’ll have the rocket stove guts layed out and working. Most of the guts of the stove are going to be below floor level, so I gotta build the stove and the foundation together.

Ok. Today I built the platform that the stove will sit on and insulated underneath with pumice. I chose pumice ’cause I’ve had it laying around for some time and it was a freebie, also I expect that it will encounter moisture occasionally. Seems to me that pumice will handle a periodic wetting better than perlite or something like that. Today I also built and tested a quick-and-dirty 6 inch rocket stove on the platform. It felt right, to gauge system size by just making one and staring at it. It seemed to me, (after fiddling with wet wood in a wet 6″ stove on a gusty day) that an eight inch system will likely be more appropriate.. So tomorrow, I tear it all off and build an eight inch system in it’s place.”

Read the rest at the source: Sauna Project

9 thoughts on “Straw/Clay Sauna”

  1. I would be surprised if strawbale saunas have a consistent lifespan. There are so many variables to how long one might last. Quality of construction, diligence of maintenance, how much steam is used when under operation, how often the sauna is used, quality of exterior water proofing, climate, etc.. etc… etc…

    That doesn’t mean it would bed uninteresting to find out what lifespan strawbale saunas have achieved.

    As far as the door for this sauna goes, the smaller the door, the better the heat retention as someone enters, exits. Instead of crawling inside, it appears that someone opens the door, sits down on the threshold, swings their legs inside, stands up inside, and then closes the door.

    I think a two door airlock for a sauna would make better sense. It would be good for heat retention, and prevent that cold rush of air on any occupants the moment someone else enters or exits the sauna. Either that or a revolving door, which would be unnecessarily complicated. Think of the airlock as a small enclosed porch. One might even utilize that space with a small bench to sit on to change store mucky shoes. It would help keep the sauna clean, which is extremely important. Might even be possible to have the airlock serve as a shower stall. It always feels good to wash off all the sweat after sitting in a sauna. Could probably even collect rainwater from that roof for the shower, and maybe even heat it from the rocket stove.

    Of course, a shower in the airlock kinda reminds me of that shower on the strawbale balcony Owen posted about a week or so ago. It would be critical to waterproof the shower well and drain the runoff water well away from the strawbales.

  2. While this looks interesting and I’m definitely interested, I dont understand why it needs a roof. Is it because it will wet the mud and crumble the sauna eventually? Also, one other thing. How do you get in through the door? It looks like you would have to crawl into it. Is that right?

  3. Cob/adobe/earthbag interior walls fully cured then wrapped in a strawbale or papercrete exterior blanket might make the best of water protection and sauna insulation.

    Clearly you don’t want the insulation getting wet. Either from rain on the outside or from steam from the inside.

    Scoria filled earthbags would be a great option, where available (I’m guessing scoria is not plentiful in Scotland, so that’s probably not going to happen there.)

    If you think about it, this sauna is really just a really huge rocket stove powered oven.

    Aprovecho has proven Scientifically that the most efficient rocket ovens are small, low mass, and well insulated, especially when used intermittently. High mass ovens only makes sense when constantly in use, like in a commercial bakery.

    Applying this data to saunas, it seems that if the sauna will be in use 24/7, than an insulated high mass design would work. However, that is pretty rare for a sauna to get constant use like that.

    The low mass high insulation option seems appropriate for most situations, IF the the design keeps the insulation dry. That’s a huge IF.

    In some respects this can be a choice between fuel efficiency and structure lifespan.

    A super cheap easy to build strawbale sauna that may need to be torn down as the bales begin to mold, compost the old straw, and replaced every few years might be a practical option in some situations, especially if someone grows their own straw and has plenty available.

    That can be a huge advantage of working with all natural materials. No waste when it’s time to replace a structure. Just more compost to feed the next crop of straw to build with in the future.

    • Strawbale saunas can last for years. I’m sure we can track down some examples. It would be interesting to learn how long they last.

  4. Hi Owen, this sauna looks amazing! I live in Scotland and am going to try and attempt something similar. over the winter. DO you have any tips? Is it solid cob or is there straw in the walls also?

    • Straw/clay has a higher percentage of straw than cob. Cob or earthbags would be more suitable for a sauna since they would be more resistant to water damage.


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