Konnichiwa! I'm new to this sight and have a complex project which I am looking for some shared insight on. I've reviewed a great variety of info and read the book by I think Iantos, but still I am coming to all of this pretty fresh.

My partner and I are settling on a 100 year-old farm house on an island called Etajima off the coast of Hiroshima. This is significant to the topic for the reason of Traditional Japanese rural design attributes. 1. Most of the house "living space" is on stilts about 2 feet off the ground 2. This is adjacent to a roofed entrance which spans the house from front to rear and this section is at ground level with a soil floor. 3. these houses are by nature poorly insulated and of very mobile interior structure supported mostly by posts with movable walls on tracks. This combination, from my perspective makes these houses excellent candidates for rocket mass heating "systems" (I'll explain my use of this term shortly). The thing I do not wish to create is large cob benches or beds as I do not want the obstruction of a this type of mass in a Japanese traditional house, but rather I am interested in designing a multi-function system which uses mass in place of some sections of Tatami by removing a few of them and building from the ground. OR possibly putting tatamis on the clay.. might be possible...

What makes it a system is that what I would like to do is create the following: 1. Heated floor sections, possibly more than one 2. water heating system 3. Oven 4. sauna

I would like to accomplish this with as few parts as possible and:
- I must be able to control which parts are being used or not, such as I want to bake bread, but I don't want to heat the bathroom floor..
- The water heating system would likely supply additional floor heat as well as wash-water (how can I control the tap delivery temp to prevent scalding?)

Right now my best guess as to how to multitask this type of system is to put the stove in the ground level area just next to the main living area. The main exhaust would go through a mass underneath this part of the house. I'm figuring on putting a water tank directly attached where the stove is and forgoing direct cooking surfaces. My understanding of how to do the oven would be to run an exhaust pipe from the Stove to the oven and then I guess I could give it its own direct exhaust if I don't want to heat the floor... so basically make a boiler, and run 2 exhaust systems. use the standard stove design for the floor section, create a lot of hot water... some kind of switching system of sliding steel traps could allow me to choose where main exhaust hoes and thereby what would be heated.

In a crude way I can see how to get it to work... but it's a kind of Frankenstein still. Attaching the sauna to it seems to be very tricky. The hot water needs to be earthquake proof. I would need hydraulic pump to heat alternate floor sections most likely.. I am considering the idea of splitting all of the functions into 2 separate units.. but I am very interested in the possibility of using 1. I'm interested in connecting with experienced people on this topic as well as other possible shared interests

Thanks!

*It is worth noting that this place is being created as a design and educational destination as well as showpiece. We're preparing a program that will connect with agriculture, herbal medicine, eco-touring/biking, woofing, foods/cooking/health, yogic and other ancient practices which we will be hosting as well as leading in some cases.

Hey, Brendan, welcome to Permies! This sounds like a fascinating and challenging project. I'm not a person who can give you useful feedback, but I'm bumping this up to see if anybody who didn't notice the topic two weeks ago might want to chime in now.

Thanks! I couldn't even tell if anyone had looked at it. We have the house now and have started cleaning in out and checking over the condition of things.. We have some 50 kilos of fermented foods left far beyond their freshness date which I am devising the best way to compost...

Welcome to Permies, Brendan!

As you do your reading and designing, pay special attention to the TIME element of 4 different functions for the Rocket Energy system. The reason that RMHs are ducted through large cob benches and beds is because they take a long to heat up when the RMH is being actively fed, and they re-radiate this heat for a long time after the RMH has gone out. A RMH is pretty much the opposite of an on-demand hot water heater!

Think of how your 4 different functions fall along the demand spectrum. You don't want to have a sauna that takes a long time to warm up. (Well, unless you are content to fire up the RMH, duct the heat to it, and wait a while.) If you had a well insulated tank, you could use a RMH where the M stood for a large mass of water. But it is likely to lose heat to the ambient environment, so that your hot water tank soon became a warm water tank.

An oven is a quick demand application. I have a RMH that I use for space heating, and I am thinking of how to build another RMH in my kitchen that would fuel an oven. I'm pretty sure that if I duct the exhaust directly from the RMH around a sheet metal box, I can make a decent oven that will get up to roasting temperatures, but it has to do that first, before it loses any heat to a large thermal mass. Once the exhaust leaves the oven, capturing residual heat is going to have to be done in another thermal mass. Then again, I'm only going to feed the kitchen RMH when I am cooking, and when the roast is done, I would want to go eat and not keep feeding it to keep the kitchen heated.

So the gist of my comment is maybe you don't want to build one RMH......maybe you want two........or three.

Thanks for the thoughts. I've come to a similar conclusion. I think what I'll do is prioritize the Sauna to be ready by Oct and this month build an outdoor biochar retort which I may experiment sucking oven heat from. This doesn't seem too tricky and allows some cheap non-dangerous experimentation. I'm interested in setting heat exchange for water tank as I've found out our water heater is dead anyway. If anyone has some thoughts on this I'm interested. I've seen a lot of copper coil water exchangers.. they seem simple to build and functional.

in sum,

1. I build a rocket stove for the sauna, which can be pretty small I think. How much concern is there with monoxide ? Or if the draft is good it should be ok?

2. I build a retort chamber outdoors. A friend of mine showed good water heating from this... an attached oven compartment seems pretty simple to experiment with though eventually I'll be building a dedicated oven. I'm not sure how simple it would be to get a retort to double as water heater in any ongoing manner. I'm interested in suggested retort designs for sure.