I see some designs for rocket mass heaters on the internet and I found them very interesting as a sustainable heat source.

In a normal wood-burning fireplace, the chimney needs frequently cleaning. But in a rocket mass heater, the outlet pipe has several bends, so how can we avoid blocking the chimney outlet and how can we keep it clean?

  • 1
    can you include a picture/schematic that shows the bends you are mentioning?
    – mart
    Jul 1, 2013 at 8:38
  • Also, when skimming the pics. in the rich soil article, I did not see any way to add secondary air. Are you sure this is a well thought design and are you sure the issue you mention is actually adressed?
    – mart
    Jul 1, 2013 at 8:48

1 Answer 1


Chimneys almost never clog from soot/creosote buildup, so your assumption is flawed, but thick buildup is dangerous because of the potential chimney fire.

A well-designed, well-managed rocket mass heater will produce a tiny fraction of the buildup of a conventional woodstove. So the concern is minimized.

You can build a cleanout at each corner to let you reach in with cleaning tools.

  • Just adding some info to what JB said, Rocket Mass heaters raise the combustion temperature higher than a regular fireplace causing greater separation of volatile compounds (more fuel actually burns). Additionally, most increase the air/fuel ratio lean of stoichiometric significantly reducing particulate condensation. The result is a, "rocket mass heater will produce a tiny fraction of the buildup of a conventional woodstove".
    – OCDtech
    Jul 12, 2013 at 17:10

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