Rocket Mass Heater

A rocket mass heater is a clean burning, high performance heating system. Although it is similar to the rocket stove and masonry heater, the rocket mass heater contains chambers designed to draw exhaust horizontally before leaving a vertical flue or chimney. This creates a thermal store large enough to retain heat for many hours.

With Max Edleson from Firespeaking, we built a rocket mass heater for the wall tent to provide heat for campers during the winter months.  To begin, we laid out the shape of the bench using urbanite, thus being the first layer.  Next, we cobbed, added another layer of urbanite, and cobbed.  Pipes are laid out and connected using high temp aluminum foil tape.  Make sure there were enough accessible clean outs.  The heat riser is built using fire bricks with an earth mortar ( 1 part clay slip to 1 part sand).  To prepare the barrel, we burned it to remove any paint and sealed the lid using rope for a tight fit.  The barrel is then placed over the heat riser and a cob mix with heavy straw is used to connect the space between the bottom of the barrel and the pipe.  It acts like a bridge. We cobbed around and over the pipe until a comfortable seating height was attained.  Setting a fire will help speed up the drying process and then a base plaster can be applied.

Graphic from permies.com showing how the system works

Graphic from permies.com showing how the system works

understanding fire

understanding fire

laying second layer of urbanite

laying second layer of urbanite

IMG_2255

cobbing around pipe

cobbing around pipe

clean outs

clean outs

building heat riser

building heat riser

gluing rope in barrel lid

gluing rope in barrel lid

first fire

first fire

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