I'm considering building a rocket stove mass heater inside an attached 2 car garage and running the exhaust pipe and cob mortar bench under the house. The space under the house is 50 feet long X 30 feet wide X 3 feet high. My plan is to run the exhaust pipe surrounded by cob under the full length of the house, make a wide u-turn with the exhaust pipe and run it back the the full length of the house again, then out through the side wall. This would make the overall length of the exhaust pipe about 120 feet. My idea is to install a few vents in the floor of the house so that the heat from the exhaust and cob bench under the house will rise through the floor vents and heat the house. I would like to get some input about this idea, especially about the length of the exhaust pipe and the radiant heat rising from the mass of the cob bench which would be around the exhaust pipe under the house. By the way, the crawl space under te house is insulated.