Cookstove + Masonry Heater Hybrid

The impetus of this project is to create a single unit that combines a functional cookstove with immediate heat production with an efficient firebox for prolonged masonry heat storage. We will draw from medium-sized “batch-box” development and use bypass dampers as switches to significantly alter the flow through the heater depending on the output desired.  An important part of the project will be to experiment with an open-source flow for project development. This project is being developed in the context of a hands-on workshop that will be realized at the Masonry Heater Association’s 2022 Annual Meeting.

Here is the initial volume concept:

Here is the most recent drawing set just completed!

I think that the middle version is probably the most applicable but the workshop context of this initial heater build calls for a large amount of bench space as warm sitting space for conference attendees. This is why the bench version is the one developed here.

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  1. I like this idea, kind of the best of both worlds. Can we add an oven too? Half joking, probably adds too much complexity. I am planning out a small, approx 500 ft^2 home (300 footprint + loft) and would love to have something like this in it. Eagerly awaiting more discussion. And willing to be a guinea pig if one is needed. Home size might be borderline too small to need that kind of heat, but it’s a cold climate so maybe it’s worthwhile…

  2. Avatar for max max says:

    @FerryCounty, I am just in the process of working on the design, and have tentatively added an oven and am planning on hot water heating too. Stay tuned, I will try to share some screen shots shortly. Indeed, I am hoping to get rolling on this project.

  3. Avatar for max max says:

    Before preparing more technical sections, I wanted to share the process of conceptual design… exploring different variations, mainly with a broad conceptual view in mind but trying to keep the technical inner workings as I evaluate each stove option. Here are some different variations on this idea. I think I would like to settle on the one at the end and will begin to draw out the inner workings. Interested in people’s feedback…

    Just about the simplest cooktop and mass combination… possibly not enough room for the channels we would need…

    Full-blown, large wood-fired oven…

    Kind of classic but requires a custom cooktop…

    This is the one that I would like to detail:

  4. Avatar for max max says:

    Here is a little more detailing on the concept sketch, also showing my hope that we can include a hot water heat exchanger that thermosiphons to a hot water tank.

    Here’s the SketchUp file if anyone wants to play around with it or insert it into a home design:

    Cookstove and Masonry Heater Hybrid (SU v2021).skp (1.7 MB)
    Cookstove and Masonry Heater Hybrid (SU v2017).skp (3.6 MB)

    The next step is to start drawing more technical sections showing the flue paths.

  5. Avatar for max max says:

    Anyone have any votes about how best to name this project!?

    Vote in the poll.

    Suggest other names and I’ll add them to the poll.

  6. Max, I have always found the 9"wide or so firebox of most cookstoves to be limited on how many channels you can add on to them. So we normally will use one of our standard 13"w x 18"d fireboxes and add a cookstove top above the firebox and then vent the exhaust out the side of the firebox into a down draft channel and a large bell or just into a large bell. Kinda like the MHA workshop we did 2 or 3 years ago. Below are 2 photos of a simple bell on the side and a more complex bell.

  7. Avatar for max max says:

    @SolidRock, it’s an honor to welcome you to the forums. For those who don’t know Eric, he is one of North America’s most accomplished masonry heater builders.

    Indeed, I am planning on a slightly larger than normal, for a cookstove, firebox and importantly for the main combustion route to lead into a significant heat riser which I am hoping will produce the kind of thrust that we see in rocket mass heaters. I should have some sections done within a week so that the inner workings will be more understandable and open to critique and response.

  8. Max,
    I look forward to this. I will have to look at getting a link up on my website for this forum so that others can see it, learn and contribute.

  9. The Heat n Eat (alator)! But in all seriousness, i’m really looking forward to seeing your design come to life in April. It reminds me of the first masonry heater I ever saw, at Granja Valle Pintado back in 2011 with a small water tank up above for hot water heating and a lounge-y heated bench… I became infatuated with the idea of hot cob!

  10. Avatar for max max says:

    Hey, hey! Welcome Jim! Another great heater builder joins our ranks!

    Indeed, once you get interested in masonry heaters, especially from first-hand experience, that interest tends to continue strong.

    I love the “Heat n Eat (alator)”! Just now realizing I can’t change the poll after it has been live 5 minutes.

    Yes, looking forward to further developing the design. Stay tuned!

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