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Officially, a Rocket Mass Heater?

So, we have this ... thing ... in our living room. Pictures of The Thing

We built it out of recycled bricks, metal, sand, dirt, and a little bit of fancy stovepipe, tile, and plaster.

It burns wood. But it weighs over 6000 lbs, so officially it does not qualify as a woodstove. We gave it a factory-built chimney suitable for a woodstove, and some heat shielding and insulation from the walls like a woodstove, anyhow.

At that weight, and given that it's mostly made of masonry, it might be a masonry heater. (These are exempt from UL testing according to the testing companies and masonry heater guys. Oregon building code finding 93-47.pdf describes a type of European masonry stove, and it seems to apply pretty well to what we have here. Except for the shape.).

Our Thing is spread out around the room, about 18 inches high, and has a factory-built chimney instead of a masonry chimney. (A masonry heater is usually a giant stone or brick chimney, which puts the smoke from a fireplace or woodstove through some baffles to slow it down and collect more heat from it. Masonry Heaters Association,

Does it need a reinforced foundation, if there's no possible way it could fall on anybody or bring the house down with it?

It can boil water. But it's not our sole cooking device; we use it occasionally for making tea/soup, for fun or in power outages. (A cookstove that is your only way to cook is exempt from EPA even if it smokes like a demon.)

It can heat the house pretty well - it was able to bring the thermostat to 61 degrees, in 13-degree weather. We have a furnace in the house, but we don't use it when The Thing is working.

And it's really comfy to sit on. (Part of it is a heat-exchanger, where the flue gas runs through a cob bench, so it makes a full-body heating pad or heated sofa/bed.)

The flue gas doesn't smell like woodsmoke, or like much of anything. It's basically steam and CO2. On warm days, it makes no visible smoke. Just clear flue gas. On cool days, it puts out clear steam that immediately condenses into white clouds, and then dissolves again as it drifts away.

We've had friends over with small children, and lit it for them, and they felt comfortable and safe.

We just had two inspectors from Portland's building code team, and one from DEQ, out to have a look at it. They didn't give it a permit, but they didn't deny it, either.

It doesn't fit into any existing box.

Here's the long version of the story:

Ernie was part of the research team for the 2005 edition of the book, Rocket Mass Heaters: Superefficient Woodstoves You Can Build (and cuddle up to!). When he got hurt, we did a workshop as a fund-raiser and built one outdoors at Tryon Life Community Farm It went over well, and one of the participants had us do another workshop the following year at his house - to heat an outdoor bench and small outbuilding.

There's a lot of interest from folks in being able to build one indoors, in a "normal" house. (We have friends and mentors on Oregon's south coast, who have installed these in small cob houses where they are the only cooking and heating device, and they work great. We also know of a few people in various places who have installed them, up-to-code or otherwise, as owner-builders in conventional and/or log houses, and they work well there, too.)

We've helped people build a couple of them outdoors for a "warming fire," and they work pretty good - but outdoors is not necessarily where most people want to stay warm. The "Pocket Rocket" was developed for people who have no indoors to go to, and need a warming fire - but it's kinda bulky for most people. Ernie knows a guy who has one on his boat.

We can help someone learn how to build a clean fire, and how to clean out their Rumford fireplace so it works better(or refit an "ox-cooker" fireplace to a more Rumford-like configuration for better heat efficiency). And we can show people how to build a Thing as a fancy outdoor cooking or heating device. www.ErnieAndErica.Info We think these Things are an improvement over what's out there for home solid-fuel heating, in a lot of ways.

For example, they put out way less visible smoke that the currently available UL-certified woodstoves, even when the latter are run by competent fire-makers with properly cured wood. (With inexperienced people or wet wood, there's no comparison.)

They use about 1/5 to 1/10 the wood for heating that a conventional woodstove would use in the same place. This means a normal, suburban family could get the heat they need without quitting their day job to split wood.

They provide an extraordinarily comfortable, direct body-heating option, which means that you can have a variety of people in the house and maintain a temperature gradient that keeps everybody happy.

So we'd like to be able to tell people, "Get a permit, and you can put one of these in your home; here's how you do it to code so you don't invalidate your insurance."

But nobody's done that yet, at least in Oregon. So we don't know how it would work.

So we decided to try it ourselves.

The place we're currently renting is part of the Dana property in the Sylvan hills. It's an attached cottage, known as the Annex or "Little House," next door to "the Big House."

The family has been thinking about developing this two-family residential property into a sort of ecological retreat or B&B, to preserve its rural character in an increasingly suburban area. (Recent infill has contributed to stormwater and other problems, and the owners are not excited about the idea of seeing their childhood home replaced by 5 or 6 big-footprint McMansions.)

So Emily Dana was in favor of installing an efficient wood-burner in the rental house. She paid for the permit application and the parts required for code, as a "capitol investment," and got her hands dirty mixing cob, laying masonry, and cobbing-in the heat-exchange ducting.

We got the permit application in September, and we had the stove mostly built by the end of October. We had to wait a while between layers, because of damp (the little house is pretty damp to begin with).

Our final work-party to finish the exterior plaster was the weekend after Chinese New Year. The 180-day deadline for our first inspection was still a month or two out, and we thought about calling around to get advice ... but we decided that we'd rather hear it from the officials in charge, than try to please everybody and then hear it from the officials anyway.

So we called the Bureau of Development Services, and scheduled an inspection.

We were all excited about it, and tidied up the living room, and rescheduled our tax appointment when the inspector needed to come earlier in the day.

Inspector John came out, and said, "Wow." Or maybe, "Whoa." He looked in both ends, we lit it off for him, he asked to see the plans, we pulled out the Rocket Stove Book and our photo show, and hunted around for the original design drawings.

He said, "This is very cool - but I can't inspect it. I have no idea what to inspect it for. Let me put you in touch with my supervisor."

So we called his supervisor, Joe. The first thing he asked when he called back is whether it was a "cooking rocket," or a "rocket mass heater." Good researching!
(Cooking rockets were developed for third-world families as an improvement over a 3-brick indoor hearth; they have an L-shaped burn chamber, and are not designed to heat a home. or

We had an interesting phone conversation about whether we had a woodstove, a fireplace, or a cookstove. We said, "None of the above." He told us if it heats the house or cooks food it's an appliance (not the term I would have used for a fireplace or chimney, but apparently that's the building code language). And would need EPA approval and UL ratings. We pointed him toward Finding 93-47, which describes "masonry heaters" as an alternative category of solid-fueled device, hand-built, and not considered a UL-testable woodstove on account of the weight.

(We had already asked about this by calling OMNI-Test Labs. They certify woodstoves and other fuel-burning products. They said it sounds like we have a masonry stove, which is exempt; and also, the UL tests are run at three wood-consumption burn rates, all of which are faster than our Thing can swallow wood.)

After doing some research, Joe called back and set an appointment for the following Thursday morning, to come see it and bring a DEQ inspector along. We invited him to bring anybody else who wanted to see it, too.

Once again, we tidied up and prepared. I got all our design drawings and notes collected into a file, and drafted a new, larger drawing on official-looking architectural vellum.

Our inspectors arrived on time (Joe from BSA, Robert from DEQ, and later John stopped back by as well). We showed them what we have, and they asked to see it work, and we discussed options.

They could see the value in a "poor man's masonry stove," and Robert from DEQ seemed relieved to find himself among people who knew how to make fire without smoke.

But they couldn't pass it, based on the existing code categories.

One issue was the permit we'd gotten: it was for a woodstove installation, which means UL-approved or antique woodstoves. For a masonry heater we should have submitted the plans first for a mechanical permit, instead. (The office didn't know this, and they were between issues of the code at the time, so neither did we.)
Joe decided to keep our original permit open, meaning we'd have another 180 days to get it inspected again. We could submit the plans for a mechanical permit, and if they needed changes (like a reinforced slab footing suitable for a massive chimney) we could tear out the existing work and re-do it. Um....

Another option would be to submit the plans and information to "OMOA" (another division of BDS), and see if we could get it passed as an "approved alternative." (To my mind, this might be necessary anyway, because of the earthen masonry.)

Or it could go through testing at OMNI-Labs and get approved as a heating device, we could put a sticker on it, and they could pass it as an appliance, like a woodstove but different.

If we didn't have an electric range, it could be exempted under DEQ as a cookstove. But I kind of like having a kitchen. (My thoughts: Maybe there's an exception for emergency cooking / heating, like the woodstove Grandma used to have in her basement?)

So that's where we stand at the moment. Joe, John, and Robert are going to keep talking to their office mates, and showing pictures. We gave them Ernie's card with our website, and hopefully they can find the pictures.

We'll give Karl in OMOA a call in a little while once Joe has had a chance to mention this to him, and see what the process is for "approved alternative."

It may be a lengthy process, but hopefully we can get a prescriptive, or ideally descriptive, option worked out. That would allow a homeowner to build this "poor man's masonry stove," and burn less fuel with less smoke than any other option we know.

    The Thing's good points:
  • Clean
  • Efficient: low-fuel, lots of heat
  • Local biofuel alternative energy
  • Low-cost
  • Low-maintenence (yearly inspection/cleanout, daily ash cleanout and one or two 2-hour firings per day during cold season)
  • Safety: Lower temperatures on exposed surfaces than most heaters, fewer toxic components, fire is mostly recessed away from curious hands.
    Points of concern:
  • Foundations and reinforcement: Seems like overkill to pour a concrete slab with enough rebar to support a 10- or 20-foot chimney, when this stove is basically a slab with a center of mass under a foot from the ground. But existing slab-on-grade may not be enough.
  • Unusual materials: Earthen masonry, recycled metal barrel, and ducting/stovepipe installation specs:
    These are substantially different from approved Masonry Stove construction methods. (Masonry chimney, high-heat ceramic flues, rebar and concrete footing, hearth or vertical burn chamber door, etc.)
    We think they're better in many ways (better thermal contact between flues and mass, solid monolithic masonry with integrated tensile reinforcement instead of linear rebar, lower environmental impact and materials costs). And there's some evidence that concrete and rebar are not compatible with earthen masonry in certain applications. But it's not up to us entirely: somebody official needs to agree with us about that.

Other observations from the inspectors:
Robert wondered if a child could "fall into" or against the barrel and be burned.
The barrel is a substantially lower temperature than the woodstove we had in my home growing up, or the modern ones I've seen in other homes and meeting spaces since 2005. And we've built a fairly substantial cob structure around the stove core. It's ergonomically not that easy to get your body in position to fall into the barrel unless you actually climb onto the sloping cob mass. The kids we've had in the house seemed to get the picture quite easily, and sat happily on the bench or ran around in the other parts of the house. But it could happen; kids do run around and climb on things, and it might one day suffer the same fate as many a family sofa.

Proposed solution: John described a screen they'd built from square metal bars, three rails, that served as a "kid fence" without interrupting the radiant heat from their stove. I've been looking for decorative options anyway, and a wrought-iron lattice or sleek modern rail could add something nice to the stove's appearance. (And, Emily observes, it would be somewhere nice to dry mittens, socks, and warm towels for luxuriant showers.)

The option that Tryon Farm used for kid-safety (they host school groups, and have toddlers in residence) was
a) Ernie designed the stove so the barrel wouldn't overheat easily, and
b) they cobbed a sculptural motif around the main part of the barrel in addition, making it difficult to accidentally touch the metal but still possible to cook on it.

While thinking about safety, Joe liked the downdraft setup. It's not hot above the wood feed, and it avoids a lot of the problems associated with a "hearth" where fire can fall out onto the floor.
From our friends' experience, you'd have to do something really silly like perch a 4-foot long crooked stick of firewood in the stove (more than twice the design length), and then leave it unattended, leaning precariously at odd angles, in order to get it to fall out.

One of my favorite aspects is that we can actually burn a single log (of 4" to 5" diameter) and it self-feeds and self-regulates the air. Smokeless, just like the other fuel options.

Another speculative option that one of our inspectors suggested in a humorous mood ... would the fact that it's made of local dirt, as old as dinosaurs, and in a traditional manner, possibly qualify it as antique?

* * *

While we're blue-sky dreaming:

I have a design fantasy about creating a "Green Vent" option.
People who want to sneak a stove like this into an urban area sometimes use dryer-vent style exhausts to avoid alarming the neighbors. Since there's no smoke, or very little during the first few minutes of a burn cycle, it's reasonably safe - but you wouldn't want people breathing it all the time.
What if that exhaust could terminate in a vented "cloche" (small, doorless greenhouse)?
It would be kind of like the air handlers that sit by big institutional buildings, but instead of grey metal and buzzing electronics, it would be a haven for tropical cloud-forest plants that would soak up the CO2 and fog and grow to dinosaurian proportions.
(Carbon counts during the time of the dinosaurs were more than 10 times current levels, and 25 times the levels before the industrial revolution. Some of those plants are still around, and wouldn't it be interesting to see how big horsetails could really get in their original growing conditions?)

You wouldn't want to do this with a greenhouse that people could walk into, because flue gas just isn't that healthy to breathe. But if you could avoid people walking in during or after a burn, or enforce adequate ventilation if they do, it could be an exquisitely "green" solution.
What if you did it with a cloche or tent-style greenhouse, where you had to literally pick up and remove the whole enclosure in order to enter the space?
Or maybe just a removable wall/large access panel for a larger structure, with fasteners that require tools or codes. Dire warnings could be put on both greenhouse and heater, to avoid firing the Thing while the greenhouse is being tended. It wouldn't be foolproof, but it would be within normal safety parameters for many job sites.

A fenced-off forest plot could serve the same purpose, enhancing carbon recapture to force-grow next year's fuel.

* * *

I think you can see why we're excited about this. We're not likely to become stove contractors even if this passes, but it would certainly enhance our ability to teach people fire science and offer a clean, green, low-cost alternative for home heating.

I think heat is going to keep getting more expensive in the coming decades. A Thing like this could make a huge difference for struggling families.

Even buying all-new stovepipe, if you do the work yourself, it could cost less than a modern woodstove. (For comparison: We spent about $700 on our so far; $500-600 on factory-built chimney stovepipe, $100 on sand for this and other projects, maybe about $50 on lime, clay, pigment, etc. Our friends who duck the code can build one for about $50, by scrounging scrap metal and used brick. Other friends just got a good-sized, EPA-approved woodstove installed for about $4000, and it smokes way more than a rocket stove. A traditional European masonry heater comes installed for about $10,000-$38,000 - it's a multi-generation investment, suitable for an estate or large, permanent home. These also smoke, though not as much as your average woodstove because they batch-burn instead of smouldering.)

So wish us luck.
If you have any comments, or want to bring this to someone's notice who might be able to help, we're all ears.

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