We built this rocket mass heater in Gracie's basement in the fall of 2019. It uses a cob mass bench with a terracotta bell for the thermal mass and a standard 8" firebrick J tube core. It runs on sticks gathered from the yard and hardwood scraps from the local flooring mill. In September 2020 we checked in on it to get it ready for the heating season. Our client is very happy with her warm floors and low energy bills. For more exclusive mud and fire content support us @
https://www.patreon.com/unclemud 
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