Mike Schofield

Thanks for the replies. I think I'm erring towards the batch box simply for the heat output. But I really like the oven idea. Is it still possible? Just accept you have a really hot oven and just use for flat bread and pizza and stuff like that? If so are there plans available for that?
There is a nice tall straight chimney so that keeps options open. I'm curious how the riserless cores work? I've got my head around the insulated heat riser in a traditional rmh getting the gases super hot and burning all the nasties. How is a similar level of heat achieved without the riser?? Can't seem to find anything explaining the science '

So after finishing my first rmh last year I am now looking to my next project. I am renovating a property for friends to move into this summer and as there is only an old cast iron stove in there at present I am deciding on the best heating option for the space.
To offer a few details the house is quite small, no more than 40m2 floor space, with first floor and mezzanine. It will be well insulated but remaining quite open plan. It is an old house of stone construction.
Primarily the stove will be for space heating of course but the addition of being able to cook on it appeals too.
The questions I have are around  :

-ease of construction
-efficiency (are riserless cores as efficient as a classic batch box?)
-ease of use
-can oven features easily be incorporated into a batch box?
-heat output and retention

Thanks in advance I would appreciate any input!

Hi Thomas. Do you know how much shipping to France would be?

Yes making cob is horrible once the cold weather sets in! I find wetsuit wellies are good for stamping it, keep your feet warm and the lack of grip stops so much sticking to your feet.

Hi James. That certainly beats my piece of paper! For a very low tech fix I was quite pleased with the results, there is work to be done in refining the design for sure!
I like the grill you have there to keep the fire in place i think i might try something like that myself 👍

Forgive me if this has already been discussed. However I found that my new RMH was constantly drawing air into the fuel feed while not in use even when covered with 2 half bricks. To stop so much air being drawn in I placed a piece of paper over before placing the bricks. It creates a nice suction seal all around the fuel feed, then I place on top my half bricks. I don't have an infrared thermometer to test the temp difference but I feel it holds heat better. I will find a more permanent and fire resistant solution to my piece of paper however.

I've almost completed my first rocket mass heater. 6 inch j tube with bell bench. In general I'm really happy with it. Thing is I almost finished it, got cob around barrel and burn tunnel etc and put the slabs on for the bench. Then I got COVID and have been unable to do anything for almost three weeks now. Anyway having the rmh up and running and keeping the house at a constant heat has been great. Coming down in the morning and still having 20c is beyond my wildest dreams of how well I thought it would perform. It did smoke the first few times on start up which I was prepared for but since it dried and I've been lighting it twice a day for a couple of hours there has been no problem.
This evening however I lit it after a break of 24 hours and it smoked again.. I don't know if it will get better when I add the thermal mass ( plan is another 4inch cob on bench and slightly more around barrel) or whether I have asked too much of the system by adding a long 'flue' 'hypocaust' 'exhaust chamber' to evacuate the bell. As you'll see in the photos it runs the length of the bench.. would it be a good idea to open her up and maybe reduce that length by half before it becomes an egregious job once cob is on??
Hope it's clear enough from the photos whats going on...

Tidy work! I aspire to something as pretty for my next build. For now I'll be happy with the barrel in the living room look!

So I decided I would go with the trench idea. It's oversized as you suggested at around 8x8". A bit over to be honest. I'm now wondering whether to leave it as is or maybe skim to inside smooth. I was thinking of a perlite/lime/cement mix to insulate it a bit too.

My latest idea is to cut a channel the length of the bench at the same proportions as the heat riser and cover with bricks as in the bridge, with the gasses exiting the bench at the opposite end to the manifold. This should give to heat every chance to rise and absorb into the brick work and hopefully gain more ISA.. Good idea/bad idea?