I was introduced to the conecpt of the RMH about a month ago, love it, and know that I'm going to build one. Somehow.
Details: I'm in in a multifamily rental, can't make any mods to the house, have access to the basement, 2 floors of living space, and a walk up attic. There is a masonry fireplace, with a hearth that's supported by concrete block all the way to a footing in the basement (that's right, they have an 8 ft tall wall of CMU bumped out of the wall under the hearth, I have no idea what kind of load it will support, but it's go to be better than regular joists).
I'm going to work on an RMH in a detached shed until I deem it ready to trial in the house.
I just purchased and read Ianto's book, it's fantastic. I'll probably pick up the 4 dvd set next.
A few questions to get me started (I'm just getting started, so sorry if these questions have been asked before, I did search around before posting):
I think trying to vent up the chimney flue is a dead end, and thought about venting out the ash pit, but don't see that working well either. There are windows on either side of the hearth. Are folks that are operating in an undetected manner generally putting a vent out a window, perhaps through some rigid insulation that they've run a vent duct through and closed a window down upon?
The hearth area that could potentially support some thermal mass is quite small (2'x6') - has anyone attempted to make a massless heater with maybe some heat sink fins to radiate more immediate heat and cool the exit flue?
Will there be issues with drafting/blowback if the flue length is short (like <= 10ft)?
I know I'm going to have to experiment a bit, but before I do - should I be looking into other options? I'd like to persevere here, since I think I'm in a pretty typical end user situation, if this doesn't work for me I don't think it bodes well for mass adoption (no pun intended)
Whatever I come up with needs to be removable and not too heavy, so maybe a small version of Paul's pebble filled mass?
North America, Zone 7
1600+ chill hrs avg / yr.
45" annual rainfall
If you don't want the weight, look into big metal bells. They can be of any size and shape, and don't weight much.
My workshop heater is a batch rocket in a 500L water tank.
You can also look at Peterberg stacked barrels one. "near pish easy to make"
Horizontal batch rocket made out of insulating firebricks don't weight much. You can do most of the core dry stacked. And bell wise they can cope with 60sqf 6M² of internal surface area (isa) for a six incher. You can find some home heating fuel or tractor fuel tanks which instead of round can be square/rectangular, and a 1000l, common in europe are usualy quite near the required isa. Square type can have bricks, concrete blocks, cobble stones, pavers or whatnot, dry stacked on top and on the sides for a little mass. I advise to butt the back of the tank against a massonry wall. And for less weight also for quick heat, leave the front bare.