BTU's are a factor of the wood not the stove. An Rmh puts off the same amount of heat as a normal
wood stove with the same size of fuel load. the mass absorbs the waste heat. then re-emits that heat in the house. so if the combustion of the wood is butting off 20,000 btu and you are emitting in radiation about 10,000 of those btu's and the mass is absorbing about 9,000 and reemitting about 7,000. ok this is just rough because lots depends on temp of mass, emitting surfaces, inside temp of house, outside temp, type of wood, condition of wood ETC. the math is not esoteric just the variables. Erica and I are working on the maths that will work for those figures but there is a change between the way steel emits and masonry emits.
now most of our designs have the exhaust at the last 90. the one that goes vertical at 100 degrees F. this allows for you to be able to burn your stove into the shoulder seasons.
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Ernie and Erica
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