Building a Rocket Mass Heater for the Straw Bale Roundhouse

In the summer of 2013, we started work on the straw bale roundhouse, through a week long workshop we taught, near Millarville, Alberta (read more about that part of the project here). This is the next part of that project.

In June 2014, we taught another hands-on workshop, the Rocket Mass Heater Intensive (read more about the final stage, the Complete Earthen Floor workshop here, held in June 2014) which took the straw bale roundhouse to the next level of cozy.

Rocket mass heater? If you are wondering what/ why/ where/ how, perhaps take a look at our introduction to rocket mass heaters here for a more in depth explanation.

Some General Details

Because of the shape of this building, it was a really good opportunity to try a uniquely shaped bench that would follow the outside curve of the wall. We set to work, drawing up a plan, and calculating stove pipe requirements, chimney, and number of bricks.

We covered a quite a bit of information over the two and a half days, but the fantastic result was that our students learned about an appropriate technology that they can put into practice, heating themselves, or perhaps their green house, with an efficient and effective system.

On Friday evening, we all gathered at the Dirt Craft headquarters so that we could all experience two different working rocket mass heater systems, one in our workshop, and one in our office.

On Saturday, we met at the workshop site, and got started putting our brick layout together, in place. Sunday started out with a nice breakfast for those that camped overnight, and we got to it right away, placing the barrel in it’s final position, and successfully testing the system before we began cobbing in the bench.

  • We decided on an 8 – inch system for this space, mainly because the use of this space will require that it warm up fairly quickly, and the winters in the area are long and cold.
  • The horizontal run of the stove pipe in the bench is about 32 ft.
  • We designed in a clean-out and ash pit right beyond the barrel, for easy access to clean and inspect the manifold area just below the barrel. There is also a clean out/ inspection port in the centre of the bench, and at the very end as well.
  • We were extra careful about heavily insulating between the wall and the bench to prevent heat loss through the exterior wall, and to keep the tempperatures down to protect the bale walls from excess heat.

Below are our favourite photos of the process, from start to finish. Enjoy!

For more information about rocket mass heaters, visit our resource page here, for upcoming workshops, see our current schedule here, and stay in touch, sign up for our newsletter on the right hand column!

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