Glenn Herbert

One question that might help suggest an answer is, is there a slope from side to side in the area you want to build these rooms? If you make the first one, then the next and the next a step up or down, you could make the roofs nest over or under their neighbors, and potentially allow a pocket in the first wall for the beam of the next to slide into.

A wood stove has a much higher exhaust temperature and thus much more draw due to the chimney than a RMH will. You want the chimney to be as smooth as possible to minimize drag. I can't say if the corrugated pipe will or won't work here, but I would be cautious.

"Mediterranean" and "cold at night" says to me that you don't want any thicker mass than absolutely necessary, so you don't have an evening fire heating the space in the middle of the next day. I might do the strip of insulation down the top of the barrels to minimize a hot spot, and consider pavers of some sort down the center of the bench to allow a thinner top than just cob could reliably do.

I'm curious where the exhaust pipe draws from. If it opens to the near side of the core, gases from the bench area would have to (at least mostly) rise back up over the core to get to the exit, making flow to the bench anemic. If the exhaust goes under the core, then hot gases will hardly get to the near side, reducing the effective ISA as if that section of wall was floor.

Having a good gap around the back or under the core would allow the whole bell to act as a single unit. I think 2" would be the minimum, and 3" would be better.


Looking closer at the pictures, I see the pipe ending just at the wall, which would really reduce the effectiveness of the bench, and the core actually touching the brick bell wall. I think, given the footprint already established, your best move would be to elevate the core a couple of bricks higher and leave a large space for cool gases to travel under it freely.

"Exposed bedrock" can mean many things depending on the type of rock. Some like shale might be fairly easy to quarry or pull up chunks, while others like granite would be totally impractical to modify without specialist tools and knowledge... and a whole lot of energy

I used a 1:1.5:3 rule for my J-tube, with a 24" burn tunnel and thus an 8" roof. It works excellently and as far as I can tell gives plenty of mixing.

The dent appears to be next to the manhole in the top, so you can probably just reach in and push it back out. If it is meant for burial in the ground, the dent may have weakened it enough to be a concern, and should be reported.

Peter's original Shorty experiments used pieces of kiln shelf for the top of the firebox and expansion chamber/riser.

It sounds like you could make a hatch cover that you could open when you want to use it, with something like plexiglass in it to let light through. That could also make it lighter for ease of use.

So the point is, does the stairwell need to remain usable all the time, occasionally, or can it be sealed for winter?