How to build a Super Efficient Portable Rocket Mass Heater from reclaimed and repurposed items and save up to 80% on your heating bills


This project goes over the build of a homemade efficient rocket mass heater that is portable, uses less fuel, and burns clean. This heater is made out of reclaimed and repurposed materials. The cool thing about a rocket mass heater is that it stays warm long after the fire is out.

The whole thing is powered by a rocket stove, which is a j-shaped burn chamber. Fuel goes in the short side of the J, the fire burned sideways and the bottom of it. And then the draw is created by a tall vertical heat riser.

The gases then come out of that chimney and go all around the inside of the barrel, and a lot of the heat is given off into the room right off of the barrel. That’s your radiant heat source for the room. The barrel acts as that radiant heat source. The gases then go through a valve in the barrel down below and through a series of tubes that are encased in mass such as aircrete or cob. The gases are able to shed the heat into the cob. And the cob stores it as a thermal battery. The gases make their rounds through the tubes and go out through the exhaust pipe.



The rocket mass heater shown here is made of a burn chamber, heat riser, bench for containing the tubes, the exhaust pipe, and an insulation refractory material like aircrete which is a high-temperature cement mix. The burn chamber is made from an old sheet metal pressure tank and a stainless steel water heater tank. The pressure tank insulated with aerated concrete sits inside the water heater tank.



The combustion or gasification chamber is connected to the heat riser chimney through a three-inch pipe insulated inside a six-inch pipe. This pipe is also insulated with a refractory mix. The vortex chamber is connected to this pipe.

The vortex chamber is made from a saw blade and a leftover piece of pressure tank material. It is insulated with refractory material. Six glue stick 3/8th inch air holes is drilled at right angles around this refractory material that creates a vortex extra air suction effect. So as that heat comes up and creates a negative pressure up the riser, it swirls around the vortex chamber and enhances the burn.

The initial combustion creates enough heat to release way more gases than it has oxygen to burn. By introducing a vortex air intake system, the burn output is amplified.



For making the insulated heat riser, we are going to use an aerated concrete refractory material called aircrete . We make the mould for the four-inch heater riser using a metal mesh fabric, sarnafil roofing material, and a thin gauge wire. Then it is filled it clay sand up to the top . We take this mould and put it inside the six-inch stove pipe and pour aircete through the sides all the way up to the top and let them sit to cure.

We pull the sand out of the center of the heat riser. And then eject the liner that went against the inner fabric webbing that acted as a mold for the aircrete.

The Aircrete heat riser is installed on top of the vortex chamber. The heat riser is double insulated with an old water tank and an old 55 gal oil barrel. Also, the water tank is insulated from the 55 gal barrel using some pea gravel.The insulated water tank has an outlet pipe at the bottom for extension into the mass bench.



The exhaust pipe coming out the insulated heat riser has a two-foot drop to a directional valve connecting two pipes, one pipe acts as a flue chimney that goes out into the outdoors through the window, and the other goes into the mass bench. The valve allows us to redirect the air to pass to the bench once the heat riser is all warm.

The eight-foot-long wooden mass bench houses the six-inch stove pipes coming out of the exhaust of the heat riser. It has a mylar reflective insulation sheet on the floor. This helps prevent heat escape through the floor. The mass bench is then insulated with pea gravel which absorbs the heat and holds it and slowly radiates out over a period of time. The pipe coming out of the bench goes out of the window through the valve.



The flue chimney pipe that goes out through the window to the outdoors is made of double-walled stove pipe. A five-inch pipe is inserted inside a seven-inch pipe. The space between them is insulated with an aerated concrete refractory material.All this insulated exhaust pipe is doing is taking and adding an element of acceleration up the chimney to negate the net negative you get from dropping two feet down into the bench from the heat riser.

Image Credits : Honey Do Carpenter |

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