Rocket Mass or Masonry Heater also driving radiant floor heat.

I have not been able to find anyone doing this. I have a  house that is not very conducive to a mass heater heating the whole thing unless I put in two heaters.  Its 30 x 70. The idea occurred to me  that if I put a water jacket coil in the heater some where it could circulate the hot water via thermal siphon possibly. This would allow me to use one heater and not have to worry as much where I put it as the options for placement are limited anyway. This seems like it would be more efficient at heating the whole house with one of these heaters extracting every last BTU out of them.  It eliminates the need for a pump. Although you could use a solar pump  or at least as a back up to move water faster. I am a bit surprised to not find anyone doing this or at least tried it?  

Just wondering if anyone has done anything like this? It looks like I am going to  have to figure it out myself and start testing it unless I missed someone out there doing it and willing to share what they have learned? Any thoughts?

I'm not qualified to tell you whether or not that's a good idea. I've never built a rocket mass or masonry heater.

What I do feel qualified to tell you, is that when liquid based radiant heat is installed in houses, the water is pumped by a circulator pump, on fairly short loops to keep the temperature even, so it won't wreck the flooring above it, and keeps the room relatively well heated.

Another challenge you'll have to figure out is keeping relatively low temperature water (120 - 180 degrees F ).

I suppose if you pump it fast enough around the water jacket that might not be an issue, but it's something you should be aware of.

If you want to check out the commercial products you'll have to either buy or imitate in some manner, check out Uponor, I've designed projects using their radiant ply before, though to the DIYer gypcrete is probably going to be much cheaper.

The project sounds cool, if you go through with it please document it.

I'm actually doing that, having designed the house with a radiant floor and later discovering RMHs

I have two coils of flexible 1/2" copper wrapped around the barrel and a small circulating pump.

I have been told the cheap ebay pump I bought doesn't last very long , but using it as circulating on the cold water side and within a few feet horizontally it seems to do a good job.
I regulate it with a thermostat turning the water circulation on and off to keep the water in the coil from boiling, and keep the system open ie: depressurized so the worst that happens is the thing boils over and out through the shower head in the bath tub.

Explosions (or pipes bursting which is more likely but could still ruin your day) don't happen, although once I had solder melt out of a joint when the pipes ran dry.

If you're using a RMH with a small open firebox, a bucket of sand nearby could become very useful if you needed to extinguish the fire quickly.

An aluminum foil jacket helps the coil heat faster, and I have often thought about taking the sheet metal skin off an old water heater and using that as an even more protective shielding on top of the coil )-- heating hot water can never have too much protection/ backups. If you don't already know a fair amount about plumbing and safe methods of heating water, this is not something you should try at home

My experience would suggest that if you can possibly use the more passive exhaust ducts through the mass it will be a nicer experience with much less maintenance. Some heaters run the exhaust through  mass in the walls, and replacing center walls with this style of thermal mass might be an alternative to benches.

Radiant floors are nice, but end up with high maintenance,  (thermosiphons won't send water through a radiant system),,and hot water takes lots of btus, so you will likely need something more like a batch burner than an RMH Which is what I'm in process of converting to now after running an RMH for about 3 years.  It just takes lots of time and energy to split small sticks and keep  a fire going with constant attention---and my house uses very little heat to start with.  My batch burner is still under development, burning quite dirty now, but the relief from splitting everything down to 1" or smaller,  and having to check it every ten to 15 minutes to add more wood makes it worth learning about.

More and more I'm trying to put things on automatic using less of my attention--developing a hot water system with an RMH can be done, but ultimately there are easier safer ways to heat a house.

Or at least that's how I see it

Thank you for the replies so far.  Glad someone is already doing it. I had hoped some one was to help with the learning curve. Gives me some things to think about already. So thermal-siphon won't circulate water in a radiant system? Why not is  to far with all the pipe?  I looked at some of the threads on hot water and Geoff lawtons video of rocket hot water heater I wonder how he is pumping water in his system? Just a thought popped into my head I wonder if  a ram pump could be designed to work with thermal-siphon to pump water through a system  Probably be easier to just go with a solar pump. Keep it coming  my friends.

No, ram pumps are a whole different application.

Does your house already have a radiant floor system installed?

If not, it would be good at this stage to explore the cost and labor involved in just getting the house ready for this sort of heat distribution.

I don't think an underfloor radiant system would work well like this, but running (large diameter) piping from heater up at ceiling level to wall radiators and returning below the floor might work.

I would locate the heater as centrally as practical, to minimize the areas that need remote heating. Using a tank embedded in the mass or enclosed in a bell would lessen the risk of boiling and overpressure. I would absolutely use an open system for safety.

Underfloor radiant does work, but if it's not already installed it could be a whole lot of labor and material.  The radiator system would be cheaper and easier to install.

I think a batch burner is pretty essential, and the idea of a separate water tank inside the Bell is likely one I will adopt on my next rebuild.  It is lots less plumbing, and old water heater tanks are everywhere, just strip off the shell and insulation and no need to spend hundreds of dollars on copper pipe for a coil.