I've read several articles about these massive stone structures and you can heat a house with minimal wood, around 1.5 cord for a winter.
You can't violate the laws of physics. You need a certain amount of BTUs/hour to keep a certain structure at a certain temperature; for a given burning efficiency, that requires a certain amount of wood.
The thing your refer to is called a Russian fireplace; the idea is that the house is built around this massive thing. There are two advantages, because the enormous thermal mass means that you needn't have a fire continuously burning. The idea is you burn an intense fire perhaps once a day. This is obviously more convenient. The fire is also likely to be more efficient than a slower smoldering fire. With the advent of modern catalytic stoves, that can burn extremely efficiently at low burn rates over long periods of time, these advantages are obviated. It still seems like a nice idea though, if you can afford the cost and space, although I would still want a catalyst to maximize the burning efficiency.
Originally Posted by veremchuka
... but that is true about soapstone stoves vs cast iron or steel plate stoves. ... a soapstone stove will radiate heat longer and more evenly than a cast iron or steel plate stove.
If the "that" that is "true" is that it will use less wood, I say that's bogus for the reasons cited above.
The soapstone should radiate heat longer though, as its specific heat is about twice that of iron/steel, and thus stores (and later releases) twice as much energy when heated to a given temperature. Some of the same effect can be achieved by having masonry near your metal stove.