I live in way northern ny where minus 35 degree winter temps seem about normal. My prime source of heat is a vented monitor heater burning kerosene and anothe monitor burning propane, also vented outside. I have a chimney with good draft. I bought a coal burning pot bellied stove three years ago but the cost of nut anthracite has skyrocketed. Don't know why. I thought I had an efficient stove for these harsh winters at a cheaper rate. So now, the coal stove sits there doing nothing.
I want some thing I can fire up and leave unattended for a few hours, not babysitting it for all hours just to heat the house. I have seven rooms to heat. I have a small sand floor cellar with just the hot water heater and electrical panels there.
My first floor - floor - is wood on a wood half log joists. the walls have 3/4 pine beneath standard sheetrock. exterior is also pine sheathing under masonite shingles. voids are filled with rock wool.
It sounds like you want a batch box type firebox rather than the traditional rocket mass heater J-tube style. Look for Peter Berg's batch box in the forum; he has done some recent research with excellent results.