I posted this over on the Hearth forum, but I think it might actually be better suited for this community. I have one of those large Tulikivi soapstone heaters in my house. In some ways, it's got some things in common with alot of the systems being discussed here. It has quite a bit of thermal storgae (about 5 tons of soapstone); I can burn it once or twice a day (maybe 100 pounds of dry hardwood a day) and get constant heat out of it for 24 hours; it burns fast and hot (probably not as efficiently as a gasifier, but I am no expert on this - all I know is that I don't get much ash, no creosote, and no smoke). What it doesn't have is a heat exchanger to transfer the heat to water (it works via radiant with the room). I have radiant floor heat in the rest of the house, and am wondering if there is a way to mate a heat exchanger up to that flat soapstone surface and take some of that heat to warm the floors? The thing is in a corner, angled so that the back of the heater cuts diagonally across the corner. That back side is flat, and when it has been fired, the surface easily reaches over 120 degrees (I think it peaks just north of 150). The hx would be out of sight, but I suspect it could be done neatly regardless. Anyone got any ideas on this?