Glenn Herbert

Eight or ten chickens are not much harder to care for than a couple, and will keep two or three people in eggs full time once they are laying. A rooster can be annoying, but our experience is that they really work to protect their hens... and if you can get one or two to set on eggs, you have a self-perpetuating flock.

Okay then, it's a solid foundation for you!

A 4", 6" or 8" system means that the whole setup, from feed to chimney, is about that diameter in flow area. (Because of extra friction losses, a square channel the same size across will have about the same capacity.)

I would advise a "bell" chamber under the bed rather than tubes for the gases to flow through. See the batchrocket.eu links in my previous post for discussion of bells. This will have almost no friction losses, so it will be easier to maintain good draft.

I think the bottom of the first bell chamber would be a good place for a thermosiphon coil. Make sure there is positive pressure venting capacity, or use an unpressurized, vented system for best safety.

There is nothing about a rocket mass heater that *needs* welding. Some parts could be made with welded steel, outside of the core. If you want to make some metal containment or fastening, you can most likely come up with a bolted or screwed together design.

For a portable unit, I would suggest some form of replaceable mass, either a container you fill with rock or gravel (or sections of cob), or a water tank.

I would call it a bush rather than a tree (though maybe they grow differently in the California climate), but it would probably do well and produce good fruit. It wouldn't produce any usable wood, though - you would want other species for that..Again, I might try making mounds to start cuttings in rather than plant directly in water.

I notice your plan shows windows set deeply into the south wall. This will cause the glass to be shaded much of the day except near noon, drastically reducing solar gain. I think you would get much better results putting the glass near the exterior face of the wall.

Okay, so continental climate, a lot colder than most of the UK. I think a rocket cookstove like Matt Walker's Tiny House Cookstove would be enough to heat your structure's area, but the house's length would make the far bedroom quite cold. I think a small batch box RMH built into the wall and feeding a space under the bed would give you comfort. A 4" system would probably give enough heat, but would not be able to handle the large surface area of the bell under the bed, so a 6" batch box system with the smallest viable wall space and a large under-bed space would do well and probably only need to be fired once per day.

http://trace.tennessee.edu/cgi/viewcontent.cgi?article=1059&context=utk_agexfores


Silver maple, sycamore, and black willow all are happy with their roots largely submerged. I would probably pile up a mound of muck and stick cuttings in it for best results, though willow will take root as a broken-off twig in a creekbed.

Black willow would not be ideal firewood as it is very light, but it would burn fine if you season it. The others are decent firewood, and strong enough for many lumber uses.

As long as the piers have adequate spread footings, putting those in as described would support an RMH mass. Running the floor framing continuously across the whole floor, with just the added support of extra piers, would increase the stability of the whole system. You would then just use an air space and some insulation like perlite-clay under the core and mass to keep the floor from getting too hot (and incidentally from losing heat to the outside).

If you have soils that might settle unevenly, or are in a seismic risk zone, the continuous foundation would be safer.

I would make a section of the dividing wall doubled, with a 12" to 16" space between them, and run the heat riser up in that space. Then I would connect to a cavity in the mass under the bed for the hot gases to flow into, and from the bottom of that cavity connect to the chimney rising to the roof.

That is the bare outline; the dimensions would depend on the details of your spaces, any doorway between them, and your heating requirements. As you appear to be in the UK where winters are usually milder than in the northern US, and the spaces you want to heat are relatively small, I think a 6" system would work fine for you. For instant radiation, I would mount a metal plate in the wall of the cavity, which would also serve as an access port for inspection and maintenance of the riser. You could put a plate in each room if instant radiation is important in both. Whether you build a conventional J-tube RMH core or a batch box is up to you; in either case, you can use the information at batchrocket.eu for component sizing and cavity layout. It is generally thought that a 6" batch box gives equivalent heat output to an 8" J-tube, so you could even make a smaller size batch box, maybe a 5" system, and get good results. If you have the room, a 6" system would guarantee that you had enough capacity, as if it is oversized, you simply run it less often.

If you give more details on the heating loads and the space layout and building materials, we can give you more detailed advice.