Stone Furnace Holds Lots Of Heat

Stone Furnace Holds Lots Of Heat Doug Violette’s outside stone furnace has the thermal mass needed to keep producing heat all night long A small barrel stove serves as the furnace firebox Insulated air ducts pull warm air out and bring cool air back     “A single load of wood has been known to heat our 16 by 34-ft off-grid cabin for up to 16 hrs ” says Violette     The 4 by 5-ft furnace has 8-in thick mortared stone walls set on a concrete slab The furnace is capped by a 4-in concrete slab roof Added mass comes from loose stones piled around the firebox which is fastened to the bottom slab     “I gathered stones for about 4 years before building the furnace ” says Violette “We built a fiberglass insulated door and door frame out of sheet metal and 2 by 4’s and mounted it before building the walls We used old 2-in lumber to build slip frames for the walls ”     The entire build took about 24 hrs over a 2-day stretch recalls Violette “The stones had been stored on pallets and the rain had cleaned them One person mixed mortar while the other lugged stones into place ”     Before installing the firebox he shortened the 55-gal barrel stove by about a third He cut it off below the lower ring and attached it to the floor slab A small squirrel cage fan operates off a standard line voltage thermostat powered by a small solar panel “If the temperature inside the furnace is less than 110 degrees a snap switch keeps the fan from running ” explains Violette “There is no benefit in moving air below that temperature ”     The air ducts are 6-in galvanized stovepipe surrounded by about an inch of fiberglass insulation all inside an 8-in galvanized stovepipe The cold air pipe runs at near ground level from the cabin back to the furnace The hot air duct travels at an upward angle out of the furnace     Contact: FARM SHOW Followup Doug Violette 128 Gammon Rd Sumner Maine 04292

To read the rest of this story, download this issue below or click here to register with your account number.