science and lab results to support the claims behind rocket mass heater

Here is a question that was asked of me privately via kickstarter. I feel that the answer is going to be links to lots and lots of stuff - and I am choosing to delegate this one to the community.

He sends two notes, one after the other:

Where are the independent lab verifications of your claims? I'm down with the idea, it sounds awesome, but asking me to buy a product (or try an alternative form of heating) with sources little more than a link to a forums calculation and some clips of peoples' hands and faces in front of the exhaust vent does little to whet my scientific appetite. Make it a little more appealing to us data types, and you'd probably have a further reach.

Because honestly, I'd be a lot more likely to support this kickstarter (and endeavors like it) were I to see some funding diverted to research and development. Obviously you've done a lot of r&d, but getting metrics independently verified does a lot to bolster your case. And it is your case your selling here, not the DVDs, right?
A simple lab test shouldn't cost that much, in the greater scheme of things, right? Mostly, I'm curious about CO levels (CO2 levels as well, of course, and other potential contaminants), but the big picture question of total input to total output is the most interesting question. It's easy for me to conceive that a thermal mass heated very efficiently via wood is much more efficient than blown hot air, but how much more/less efficient is a traditional rocket mass heater than a RMH heated by, say, natural gas? Is it a toss up? Are the differences so minute as to push us towards simply collecting deadwood around our properties to warm ourselves, or is the answer more nuanced than that? Just curious. After all, there are a lot of building permits to go through for us "normalies", just want to make sure we're making the right decision here.

I like the idea that when this sort of question comes up again in the future, we can simply direct people to this thread.

I think that part of this is covered in my article. Part of this is in Peter's stuff (links?) and there will probably be 50 more links also.

I also feel a bit like saying: the anecdotal evidence is very strong. And a collection of anecdotal evidence is part of science. If you need to wait for a hefty collection of white papers to appear on the topic before travelling this road, that is perfectly understandable. It could be 20 years until there is enough to satisfy some people and until then, innovation falls into the same category as "witchcraft" I suppose. Although there are some people that are certain that taking a manned spacecraft to mars is not possible until it has been done repeatedly, and, of course, sufficiently documented in "the right way." Therefore, there are big heaps and gobs of the things that we push for here on permies that are the bleeding edge. I suppose the people doing this stuff might be viewed to be more like "adventurers" than scientists in some minds.

On the other hand: experiments are tried, results are documented and shared, and others repeat the experiment and get the same results. The documentation is less formal, but the documentation is there. I am willing to call this science - even if others would not.

Recently, Satamax asked for diagrams of full test runs. Here's a link to that thread on Donkey's board

Here are some images that back up your CO claims.

...and a full run of my batch RMH from last month. Regular evening use, cordwood, no special prep or considerations. So, an example of performance during real world everyday use.

I had a brilliant plan or at least a moderately interesting idea to use the exhaust from my rmh as a source of CO2 for my greenhouse. During the day I could do a quick burn for a hit of CO2 and at night, on occasion, I wanted to pump all the CO2 into the greenhouse to kill pests. Supposedly at CO2 levels around 10,000 ppm, bugs die and it's an easy and thorough way to kill things like aphids, mites - all sorts of pests that are hard to eradicate. In order to try out the idea, I took an empty garbage bag, put in a stem of a plant with a heavy aphid infestation and then filled the bag with exhaust air from my rmh system. I tied up the bag, left it for a few hours, and when I came back, the bugs were all asleep, but not dead. It made me think the 10,000 ppm CO2 killing bugs was an internet myth.

So, looking at your results, I don't ever see percent CO2 listed. And as I looked at both sets of results, I realized I have no idea what percent of the exhaust is CO2. I get the temperature of the stack, percent of O2 and the ppm CO, but what does % Eff qr. stand for and what is % ExAir? Do you know the rough numbers for percent of CO2 in typical final exhaust from an RMH? I get this is a bit tangential to this discussion, if you're up for responding, mail/message is fine, or, it might be nice to have that info as part of the total package of official results.

Thanks - Rick

I've been working on an article that addresses some of the efficiency considerations here: http://www.ErnieAndErica.info/rmh-efficiency
I have documented a test case in legal permitting (through a relatively friendly, local alternative technology advisory committee and appeals board) here: http://www.ernieanderica.info/rocketmassheaterpermitting

Most woodstove manufacturers allocate about $60K to develop, test, and bring to market a new woodstove model, I'm told. The current form of regulation eliminated 90% of the competition in this market, because only the big boys can afford to put out new models. And states which add their own requirements on top of the EPA standards complicate the process and make the actual problems harder and more expensive to solve.
In my opinion, the major issue that stops metal woodstoves under 900 kilograms from burning cleanly in practice is their unsuitability for the owner's intended use. Wood-burning stoves are space-heaters, and they are often sold to people who want a house-heater (for emergencies or for routine use), leading owners to operate off-book or even scandalize the stove for longer all-night warmth (after-market modifications, dampers, running a stove with its baffles or air controls jimmied or jammed, etc).

The cost of independent lab testing is about $4K to $5K for wood-burning stoves that fit "inside the box." Masonry heaters also have an approved testing protocol, but are rarely tested, because it's not required in most states. Masonry just doesn't ship back and forth to independent labs very well - if you are going to trust the builder to re-assemble it correctly when he gets it home, you might as well trust him to build it in the first place. The masonry heater protocol was written by experts in about a dozen different European styles of masonry heater, and their similarities don't extend to the J-type rocket mass heater (and the protocol may not work for batch boxes either, for other reasons).

It's anybody's guess how many tends of thousands it may cost to get an EPA-approved testing protocol that works for upside-down downdraft fireboxes, or whether this new protocol will work for the next generation after that.
Once a protocol is drafted, then testing each unit would probably cost on the same order as testing woodstoves - except for the much higher expense in time and materials to assemble a working example exactly to scale at the testing labs.

Luckily, it's widely recognized that masonry heaters are comparatively efficient and clean burning, and that moving tons of masonry to a testing lab for every site-built heater is a silly way to regulate them.
Masonry heaters are exempt from regulation by the EPA: instead, they can be instaled under section R1002 of the International Residential [building] Code (IRC). That document references the more thorough ASTM standard, E-1602.

Even the masonry heater code was not written with rocket heaters in mind.
For example the J-tube style firebox which can be regulated by hand with a couple of bricks ($3.00) as opposed to a custom-built metal door with glass insert, framing, expansion jointing ($500+). But it's a horizontal surface with a downward fire opening, so how do you define the "front" or "perpendicular to the opening" for hearth clearance guidelines?

The short answer is you can probably build one legally, right now, under the masonry heater code if you
- use a proper chimney (no getting around this one unless your jurisdiction doesn't adopt the IRC, or grants an exemption upon appeal - and we recommend it anyway.)
- upgrade to costlier, refractory-grade materials: stovepipe or ceramic channels instead of ducting (known to work with our designs) or firebrick channels and bell (use a contraflow or bell-type design, batch boxes work with these)
- allow 3 to 4 feet of clearance to combustibles all the way around the firebox.*
- if needed, have an engineer or architect on board to stamp your plans, gives the inspectors a nice CYA reassurance.
*We think this clearance will ultimately be reduced to about 12" or 18" with heat-shielding, 36" without, as for non-certified woodstoves. That would be something to run by your insurance company, local building inspectors, or the appeals board for approval of engineered plans. Right now masonry heater code offers 36" clearance for thin-walled areas, 4" air gap if the heater has thick-enough masonry (5" heat-exchange channels, 8" firebox). R1002 does not mention heat shielding, and ASTM E-1602 does it in a weird way, and only from the firebox door.

What we'd like to do, ultimately, is find a happy medium where knowledgeable people can build these themselves for less than the cost of installing a UL-listed woodstove.
That means usually under $2000 in parts (under $500 if they are lucky with existing chimneys, and can get away with using reclaimed parts in good condition).

Right now, building a to-code masonry heater costs more like $$$$$, a house-size heater may run $14,000 to $30,000 installed for a basic model. $100,000 is not unusual for fancy larger models with extra functions, or for creating one that heats multiple rooms by running heating channels through a non-combustible wing wall.
That's not affordable for the vast majority of people who might benefit from the more efficient, safer way to heat.
There are UL-listed masonry heater core kits in the 4-figure range, but they require additional masonry cladding and other materials (bringing the cost back up to very high 4 or low 5 figures), and a non-trivial amount of skill and care.

It seems almost criminal that the code and UL process inadvertently favors small, portable "space heaters" over efficient site-built mass heaters; installation price alone sends many people with limited heating resources down a path where they are trying to stay warm by keeping a fire smoldering unattended all night. Or running inefficient-but-cheap gas logs 24/7, in defiance of manufacturers' safety instructions.
It is reasonable that a process that takes more skill and attention, and creates a high-performance large object, might cost more than a simple drop-in solution.
However, installation price is heavily affected by the requirements of code. Permits may cost ten times as much for a masonry heater as for a woodstove, if you can get a straight answer about where to get them.
There are a lot of different models of site-built heaters, so the existing codes are vague enough that, while theoretically they allow expert builders more freedom, in practice they make many jurisdictions nervous, and locally-appointed authorities trying to regulate outside their personal experience and comfort level tend to get squirrelly about their responsibility, often in expensive or obstructive ways (such as requiring a footing sufficient for a 30 foot tall masonry chimney under a masonry bench less than 30 inches tall).

But it's the way things are, and proving there's a better way is going to take time and money.

That's part of why we're continuing to encourage the groundswell of interest, and help people build them in outbuildings and off-grid homes.
The easiest local approvals so far have involved an experienced inspector who gets a chance to see a working one - done to the best practice we currently know how to do.

So far our inspector experiences have been very friendly; once they see how a good one operates, they are bending over backwards to stay out of our way, or find an exemption so we don't need to go through more paperwork.
Presenting one to an appeals board sight-unseen, there's a learning curve and a plausibility barrier, and so the reports I've had are that the committee tends to throw out hypothetical obstacles, and add all kinds of unproven suggestions for how to make it "safer" or "better." These suggestions, offered as they are by people who are appointed authorities on a subject they know little about, can sometimes result in an unbuildable or unworkable stove.

I suspect it is for this reason that the ASTM standard specifies "built or supervised by an experienced masonry heater builder," rather than "engineered" or otherwise approved by a generalist building authority.

One thing I would love to do if our RMHBuildersGuide Kickstarter brings in enough surplus to play with is to do a "testing tour" of existing rocket mass heaters, and document their in-the-field performance with portable equipment.

The equipment we want also costs about $4k. Each.
The Test-o-meter emissions sniffer is one piece we want (Matt and Peter already have these)
And Ernie also wants a probe or IR thermometer that registers up to about 3000 F, and can be exposed to radiant heat hotter than that without being destroyed even if it doesn't register those temps accurately.
They may need a control box or dedicated laptop that is compatible to make lovely graphs like Matt and Peter's, with the firebox temps added alongside the emissions data.

If you think $9,000 is a petty amount of money to be obstructing progress in this field, we'd love to discuss your sponsorship of testing equipment and protocol development, for the benefit of the entire grassroots community.
Ernie and I would undertake to visit and test at least 10 sites in the next year, at cost of travel (no fee to any owner who wanted it, unless they also want some other consulting work at the same time), if someone got us that equipment this year. More if more owners are willing. We may be able to do a scaled-back version of this with Matt and his equipment, visiting our clients and his, if someone wants to cover his time.

If the most common J-style, DIY heaters can be proven to work in the field as clean as we think they do, and we document their surface temps and maybe even suggested safe clearances at the same time, that seems like a lot of progress.

I'd also like The Testing Fairy to visit at least 3 of the other models - batch boxes, shippable core prototypes, little 'uns and big 'uns. Then run with the most promising models as candidates for independent lab verification.

-Erica W

It seems to me that the first step in nailing down the rocket mass heater claims would be to find a good reference that charts temperature vs completeness of combustion for a standard kind of wood. Ideally it would be something people could point to and say "If you could run a wood stove at X degrees, Y% more energy would be extracted from the wood than if run at Z degrees."

Once combustion efficiency is known, then the amount of energy that passes from the building could be measured for a given quantity of wood run at optimal temperatures for both a rocket mass heater and a wood stove. Venting the flue gases through a coil inside of a water filled IBC tote and measuring the change in temp would probably be fairly accurate.

Rick Frey wrote:I had a brilliant plan or at least a moderately interesting idea to use the exhaust from my rmh as a source of CO2 for my greenhouse. During the day I could do a quick burn for a hit of CO2 and at night, on occasion, I wanted to pump all the CO2 into the greenhouse to kill pests. Supposedly at CO2 levels around 10,000 ppm, bugs die and it's an easy and thorough way to kill things like aphids, mites - all sorts of pests that are hard to eradicate. In order to try out the idea, I took an empty garbage bag, put in a stem of a plant with a heavy aphid infestation and then filled the bag with exhaust air from my rmh system. I tied up the bag, left it for a few hours, and when I came back, the bugs were all asleep, but not dead. It made me think the 10,000 ppm CO2 killing bugs was an internet myth.

Rick, I'm inclined to think you are looking at the wrong subject. CO, carbon monoxide, is the unstable gas that's very toxic in the sense that it supplants O2, oxygen, in the blood stream. That would be very effective to kill off bugs, yes. CO2, carbon dioxide, is the resultant of the reaction between CO and O2 and isn't toxic anymore, at all. The reaction of CO and O2 is an exotherm process and as such it yields heat so in that sense it is fuel. It's also one of the last large molecules to crack and the European rules are using this as a tell-tale sign of the quality of the burn.
CO2 won't kill bugs, CO will. CO2 is taken up by plants and make them grow so it's plant fodder so to speak.

Rick Frey wrote:So, looking at your results, I don't ever see percent CO2 listed. And as I looked at both sets of results, I realized I have no idea what percent of the exhaust is CO2. I get the temperature of the stack, percent of O2 and the ppm CO, but what does % Eff qr. stand for and what is % ExAir? Do you know the rough numbers for percent of CO2 in typical final exhaust from an RMH? I get this is a bit tangential to this discussion, if you're up for responding, mail/message is fine, or, it might be nice to have that info as part of the total package of official results.

In a combustion process, there is a see-saw effect between the combination of CO plus O2 versus CO2. More of the first will mean less of the other and the other way around. The quantity of CO2 can be simply calculated out of CO and O2. For example, 10% O2 plus 190 ppm CO means 9.64% CO2. The lower both O2 and CO the more of the resultant is CO2. That's a greenhouse gas I know that, but in free ambient air CO is reacting with O2 on its own and CO2 is formed. It will be formed in any combustion process and any fuel, by the way.

Now the terminology: %Eff gr. is gross efficiency in percentages. Without the stack loss, dry gas loss and CO2 loss, efficiency is lower by as much as 8% to 12%, also known as Eff net. ExAir is excess air, it tells you what percentage of air isn't contributing to the combustion process. For a more comprehensive explanation of gas analysing, please read this excellent article by Crispin Pemberton-Pigott.

Sorry for the side track about CO2 and killing bugs, but it's part of why I'm interested in the exhaust analysis. I get that CO is far more dangerous than CO2, but CO2 is deadly at sufficient concentrations. Around 50,000 ppm it'll knock a human out and around 90,000 ppm for a few minutes will kill a human (see the OSHA standards for CO2 exposure for workers - OSHA report on CO2 safety) Both of these concentrations are right around what you said was the CO2 content of rmh exhaust. The NIH recommends using intense CO2 concentrations to kill bed bugs and food distributors have used high CO2 concentrations as pesticides for years as well (UC Davis report on using CO2 for pest management.

What I'm just now realizing is why the percent CO2 is so much lower than I had understood in the exhaust. The equation for burning wood (CH4 + 2O2 --> CO2 + 2H2O + energy) had me thinking that CO2 was the bulk of the exhaust, but I wasn't realizing how much excess air was a part of the equation. That's part of what your meters were reading that I didn't get. So when I tried pure rmh exhaust with an infested plant and it just put them to sleep, now it all makes sense.

That article on gas analyzing you referenced was great, I get the CO2 calculation now and why the concentrations weren't sufficient for pest killing. Bummer is, rmh exhaust just isn't concentrated enough to do what I want to do. Thanks for the info and the references.

the free radicals are not good for your plants, co2 concentrations or not. and those in several cases don't recombine in the heat but after the exhaust.

testing: we have discussed putting the protocol funding as a stretch goal for our book kickstarter.

Well we knew this was coming and its here; I don't know how to answer this guy because he is asking for lab results that none of us can afford to pay for at this time if we are dedicated to keeping this in the open market. the only way to satisfy this guy is to become a mainstream commercial concern. with loans and the rest of the trimmings.

I say we put out the information we have from as many sources as we have and why we don't want this going to the commercial world. Erica has a couple grad students that have worked on this in school labs and maybe we can go that way. I do still want to take it to the testing lab in beaverton for testing and its gonna cost us. frankly i suspect it will again be Us that puts up the money out of our little budgets for the testing. Are we all ready to do that? its gonna make several of us live on a shoestring for a while but if we pool the money we can get omni labs to do the test. I suspect the next part of this discussion will be what models we want get tested. I (as i am sure is obvious) want to get the basic brick RMH tested. I would suggest we test a castable and the batch box. however peter and i need to get together and make the batch box a bit smaller so i feel comfortable putting it into a normal house. not to mention that its not been tested in use for a year.

IMO the community needs to discuss this and make a decision on the Core tech. spin offs are fine to go private but I personally dont want to see this tech locked up by some box stove company that wants to remove the competition. This will happen if we break, it's the way business is done these days.

We have all shared everything to keep our development going but none of us have been funded to do R&D! we have done it with our own money We owe no debt to anyone and frankly i like it this way.

I would suggest go look at existing RMH's or put the money where the mouth is, because we have all done that. How much more open can we be? All of the info is out there for all to see. we have not hidden anything other than (with good reason) what we are currently developing. this is not like building some new portable dodad that you can stuff into a box and ship it off to the lab.

Anyhow thats my opinion and would like to hear what everyone else has in mind. we should also get a few of the other movers and shakers in on this discussion. its much more important than just a few can decide.

hmm in other news how the hell are we going to get temp readings in the hottest parts of the stove with it fully built? we are irrigating bricks and vitrifying clay. but so far we haven't any hard temp data (well we do but folks want to see numbers in the assumption they understand what the numbers are saying rather than looking at the physical evidence). Alright i have said enough
thanks all
Ernie

Please excuse me if my comments/questions seem trite. Newbie here and just trying to break into the conversation.

I have been interested in this for a couple years, and even made attempts at building RMH. My nephew even built a test one in his house, and we got the DVDs from a couple years ago.

Is there enough data out there, and in a central enough place to sell a Kickstarter? I think that is the way to go. Certainly there are enough people interested in this question, and the more data collated for ease of use and and presented with good questions lined up and well organized can get people stoked on donating to a Kickstarter on this.

One of the frustrations I have for breaking into this on a vast forum like Permies is wading through so many pages to find the really good data and questions. It might make a good project (maybe even for me) to go through it all and put it all together the "Good Stuff". I think when this is done, it would become clearer what kinds of questions we would want answered, what kind of rendition of RMH to test (even reinvent an entirely new one specifically to test to get answers much like the USS Albacore (AGSS-569) was built purely for the sake of studying in real size a true submersible ship.), and how to build this and the cost. I think people would jump at the chance to fund that if it was presented nicely enough.

I think that the fall-over of various ceramic cones is a decent indicator of temperature. . . well, hmmmm, if you can observe the timing.

Of course, not a lot of people know what you mean if you say the combustion chamber got to cone 7 or cone 10. Still putting in little spots for setting cones would be useful. Have a little observation window? In a kiln, it's usually a soft fire brick that is set perpindicular to the others, so it sticks out and you can pull it out during the firing to (carefully!!) peer inside.

That's a whole 'nother market for this technology, you know: the many ceramic workers who are doing wood fires. Of course, a good wood firing is probably more efficient than the usual abuse of a wood stove. The fire is run at full power, there's secondary combustion in the chamber with the pots (the stuff from the wood glazes the clay after it vitrifies) and there's a good deal of mass there. When I've participated in wood fueled kiln firings, the thing runs through a day and a night at least: we have to sign up for shifts to keep tossing in wood.

(The big wood kiln at the University of Illinois back in the 80's got so hot that nails in the wood would become airborne molten globs of metal, landing on your pot and looking like bird shit. I did not appreciate the aesthetic, so I tended to not put my precious delicate carved porcelain twisty pots into the wood firings. A shame, because porcelain gets the most gorgeous orange brown color with a bit of wood exposure.)