how do we tell more people about rocket mass heaters

I just watched the videos of Paul's pebble style heaters, those are really pretty.  It might be nice to have one where you get to see it without the drying rack on it too, but it's good enough to look homey for now.  

What might make it go viral?  are cute cats the secret to internet contagion?  

A code-passing and pretty rocket mass heater would be another notch of progress for things.  I am really close, but have a technicality to finish up still.

Joshua Myrvaagnes wrote:Another thought--a video of operation of one of the more aesthetic rocket mass heaters, with cute cats?

Joshua Myrvaagnes wrote:==========================================================================================
                      You are cordially invited to


                       -- Wood Mass Heater Day --

[First Saturday in October]
at [host's address here]

Hello Neighbor,

Come visit a wood mass heater in your neighborhood.  You'll get to experience the warmth yourself, learn about codes, insurance, safety, and aesethic and cost considerations, and the impact you can have on your children and children's lives.  

Refreshments will be served.

=============================================================================================================================


This plus up-to-date info on codes and insurance policies and safety talking points, with demo of the RMH in operation.

--

I just discussed this idea on the phone with the folks at the Liberator company and they said they'll look into it, take a look at their market data/sale data I guess.  We'll see.


But people who have a code-approved masonry heater, RMH, or anything at all that is substantively more efficient than a wood stove would be welcome to participate.

If yours isn't code-approved and you're situated such that you don't have to meet codes, that is also fine.  (Actually, I can't stop anyone from holding a Wood Mass Heater Day event, it's not copyright).

I think this would go a long way toward the next leg of progress, and consolidate progress already made effectively.

paul wheaton wrote:I wonder if there could be a table-top thing that sits next to a window - and there is an exhaust to the outside through the window.  Kinda like a window mount air conditioner - but it would be a table top rocket heater.  When you are cold, you could feed it a bunch of cardboard and empty milk cartons.  

Would a pocket rocket work for this?  With a cute cabinet surround?

Re: comparison of RMH weight to the weight of a loaded freezer and suggestion that weight concerns are an unacceptable excuse for inaction.

From a bit of googling, a large restaurant-size chest freezer (6-foot long) holds about 20 cubic feet and weighs about 200 pounds. An average weight for mixed frozen foods is about 25 pounds per cubic foot. So, a loaded freezer weighs about 700 pounds total.

While the core of an RMH may weigh only a few hundred pounds, the mass needed for heat storage is much larger. The RMH heater diagram posted upthread lists the total weight of the unit as 7000 pounds (3.5 tons). This is consistent with other sources, e.g.:

CommonSenseHome Article

(From comments)
Weight varies greatly depending on the materials used and design of the stove, but a typical rocket mass heater’s masonry may weigh 3–6 tons.

TinyHouse Article

Yes, a cob rocket mass heater for the average of you know, let's say 1,500 - 2,000 square foot house should weigh about six tons. But the, the core of it that is used is the part that you have to really get right is a couple of hundred pounds of firebrick and cob and ceramic wool that you can build and then take apart and put in someplace else after you've got it figured out.

Concerns regarding the need to ensure sufficient floor reinforcement are recognized in many sources, e.g.:

Grit Article

A sturdy foundation is imperative. “I do encourage a non-combustible foundation,” Wisner says. And it should have a solid foundation below it to support the weight. A floating floor above a basement or crawl space is not sufficient.
(...)
Of course, the hefty foundation that is required to support the weight is a barrier to some who are trying to accommodate one in a home with a basement or crawl space. Revising the floor plan or adding on a reinforced space may be required.

Permies Thread

Erica and Ernie's book on Rocket Mass Heaters has a section on building on wooden floors. Basically the thing needs extra support as any mass you have is going to be heavy. Lightweight materials tend to insulate rather than store heat.

I've found some of the images look too much like physical dvds, which people aren't using much any more.  Maybe we'll do an overhaul, but for now, here is a screen shot from better wood heat, can link to woodheat.net



and here it is with some wordy bits:



and here's one we've been using for a while:

Brody Ekberg wrote:The mass is a massive amount of weight. I would guess that any rmh that is portable is also not going to heat an average sized house through a real winter. Maybe a small apartment in a mild climate though, and that is helpful. I could be wrong though, I’m not well educated on this topic. I just know that heating over 1,000 square feet of house in -30f weather will take more thermal mass than heating a yurt or studio apartment in some mild climate.

Do you know the answer to my question?

Anne Miller wrote:

Brody said, "support massive amounts of weight

What does a RMH consist of that have massive amounts of weight yet can be portable?

What parts are in the rocket that makes it so massive and heavy?

Not the barrel itself.

Anne Miller wrote:

Lina Joana wrote:Weight. I believe the fisher price house needed extra support put in. Most standard houses do not have a floor that can take the mass without reinforcement.

I feel that is just an excuse to justify that someone is too lazy to build one or just too tight to spend the money.

The only excuse that I might accept is that their insurance company will not approve and wants to exclude coverage.

If the floor of a manufactured home can have extra support added so can a standard home.  Look at the heavy freezers full of food that can be justified. I bet those weigh more than an RMH

Regarding the weight, I believe someone else answered that, but - my understanding is that yes, the mass of an rmh is a LOT heavier than a full chest freezer, unless you are storing cob or rocks in said freezer. I am sure someone on this thread could tell you the pounds per square foot number you need your floor to withstand.

Regarding the ability to make renovations- sure, on most houses it is possible. In some, it might involve getting giant beams into a crawl space or basement. In others, it might involve ripping out drywall ceilings, possibly walls if the stringers were at their weight limits. It is probably easier to do it on manufactured house, since their supports are usually accessible from the outside.
The bulk of the population would want to hire a structural engineer to make those calculations for their house, after finding a reliable number for the pounds per square inch load of a rocket mass heater at its heaviest (i.e with wet cob). Once they knew what had to be done, they would probably hire a contractor to make the modifications. In my neck of the woods, all of that would probably cost around $6000-10,000. Before even beginning the build.
I suppose you can call an unwillingness to embark on that journey as being too lazy to build one and too tight to spend the money. I certainly was, much as I wanted one. And, I am reluctant to talk it up to my friends and acquaintances as a real option, because I know that if they live in a standard house, installing one will probably not be “cheap” - not in the hundreds of dollar range that the build itself would cost, anyhow.

I just 'speed skimmed' through all of the interesting and excellent points/counterpoints here. Some random thoughts in no particular order-
-I don't think 'lazy/tight with money' is the real issue with those objections. Some people literally do not have the extra money to try something considered experimental and probably prohibited by landlord/insurance/building code. Inflation is hitting hard the past few months. And even if they have the $ and ambition, they may not have the skills or confidence. They may also (rightly) feel they are not qualified to determine what constitutes adequate support for adding maybe half a ton of mass to a floor. I suspect a typical RMH weighs much more than a freezer full of food!
-Landlords aside (that's likely going to be a 99% 'no'), Insurance is still probably the main limiting factor for most people (in the US and Canada at least) followed by building codes. My experience, and that of others I know, is that insurance companies do NOT love RMHs, regardless of lesser risk of chimney fires. They do not like anything that has a combustion flame that is not UL approved. It's that simple. And they especially don't like anything considered 'experimental' that has the name Rocket! You can tell every person possible, but when most are held hostage by insurance and codes and landlords it does no good. Once there are engineering standards, laboratory testing, consistent designs built to spec, THEN we can make progress with the roadblock of insurance and codes. That's why the Liberator sells out.
-I'm a bit confused about the idea of a tabletop or mini RMH, since the mass is the effective component. But there are some excellent youtube videos of small J-tube builds that would easily sit on a table. For quick heat in one room, something that small is probably almost as efficient without much mass anyway.
-One thing that would play better in getting the word out, I think, is less hype. By this, I mean things like an anecdote about some guy who heated his house with junk mail. We don't know how small his house was, what sort of heater he had, or if the story is even true. Beyond that, junk mail seems to have drastically declined in favor of spam email, which at least is a win for the environment. I doubt I could heat for more than a week with the small amount of mail I get in a year, junk or otherwise, including 'Amazon boxes'. The other hype that may turn people off is statements like '1/10th the wood' or 'twigs from your yard'. Most woodstoves are at least 50% efficient, so logically the most you could possibly improve on that would be to 100%, or half the wood, not 1/10th. My backyard is many acres, so I suppose I could maybe heat with all my twigs, but overall that's unrealistic for the average homeowner. Heating a house needs a certain number of BTUs regardless of where they come from. In cold areas, the minimum is probably going to be a full cord of wood, depending on many other factors like size of dwelling and weatherization. I recently spoke with a couple who just added an RMH to their fairly new (thus energy efficient) 1200 sf home in 2020, when they had free time due to covid shutdowns. The style is ranch, with a rectangular layout of 30x40. Their RMH is centrally located, and yet even with fans they cannot get adequate heat to the rooms on the ends during '20-30 below' nights (which there are many of, for anyone in northern states or Canada).
Overall they feel the RMH saves some wood over the woodstove it replaced, but does not heat quite as well/easily. They told me the biggest negative is having to 'babysit' the RMH, feeding wood in for several hours, versus 5 minutes loading a woodstove and walking away for 8-10 hours.  But they (and their cats!) love the warm bench aspect, and said they don't regret the changeover. They also mentioned that they have not told their insurance company, and realized a house fire would likely not be covered.
-The quick and cheap build, which is what is needed by people desperate for inexpensive heat, is not attractive. Our house is decidedly rustic, and yet I still don't want a burn barrel in the living area. For a year, out of desperation, sure. But long term, the typical person will choose something like the Liberator, or a conventional woodstove, even if it's slightly less efficient.
-The technology and efficiency of the RMH, like centuries of 'Russian' fireplaces, is solid and indisputable. But I honestly can't see any way of convincing more people by simply 'getting the word out'. There are literally thousands of us who would start building one tomorrow if insurance (and code) would allow it. Thousands more who would do it if a kit were available. Thousands (probably hundreds of thousands) who would have it done by an HVAC contractor if that was a possibility. I'd expect people in Europe are fervently searching for better heating options right now. Rocket stoves and rocket mass heaters are no secret. Youtube alone has hundreds of videos. I think the vast majority of those who have the time and talent to build one are likely to already know about them.
The best we can do is find ways to encourage 'industry standards' for design(s)/build so that more building and zoning departments will allow them, and insurance companies will recognize them as more than just an experiment.

Dc Stewart wrote:Re: comparison of RMH weight to the weight of a loaded freezer

Can you tell me what is inside a metal barrel that weighs so much?

Anne Miller wrote:

Dc Stewart wrote:Re: comparison of RMH weight to the weight of a loaded freezer

Can you tell me what is inside a metal barrel that weighs so much?

It is not the metal barrel that is heavy.
It is the mass - the large bench, and all the cob surrounding it the barrel- that is so heavy. Those benches in all the pictures are either cob packed around a looping exhaust pipe, or a box filled with rocks. All of that heavy stuff is what holds the heat.
I don’t know what makes something go viral. I just know what I feel comfortable sharing with my friends. And I am not going to tell them that they can build a heater for 100 bucks when the reality is very different.

Lina Joana wrote:Regarding the weight, I believe someone else answered that, but - my understanding is that yes, the mass of an rmh is a LOT heavier than a full chest freezer,

Can you point me to that answer?

What makes an RMH so heavy? It can't be the barrel.

Now we are getting somewhere:

Lina said, "It is the mass - the large bench, and all the cob surrounding it the barrel- that is so heavy.

Do all RMH use cob?

Anne Miller wrote:

Do you know the answer to my question?

Anne Miller wrote:

Brody said, "support massive amounts of weight

What does a RMH consist of that have massive amounts of weight yet can be portable?

What parts are in the rocket that makes it so massive and heavy?

Not the barrel itself.

The mass. Rocket MASS heater. Its a rocket stove with mass. Rocket stoves arent heavy but mass is. The barrel is just the stove, the mass is what radiates heat and that mass is heavy.

Brody Ekberg wrote:The mass. Rocket MASS heater. Its a rocket stove with mass. Rocket stoves arent heavy but mass is. The barrel is just the stove, the mass is what radiates heat and that mass is heavy.

What is the mass?  Where does the mass come from?

Julie Reed hits another point related to the "all-or-nothing" fallacy, that her friend's Canadian ranch house didn't heat evenly, and therefore I presume still relied on a conventional heating system...
Which is maybe another aspect to a retrofit to an existing home with existing heating systems. Zones. The existing system assumes it is doing ALL the work, and so is ironically, doing all-or-nothing, if the thermostat is in the center of the house it may be satisfied by the RMH warmth, leaving the distant rooms cold.
A retrofit might simply relocate the thermostat to sense the distant rooms, or split the home into two zones, one for the distant rooms, one for the central room, each with their own thermostats.

Fixing the "customer experience" as it were, so that folks aren't talking about their disappointment at chilly bedrooms, or the hassle finding whatever (materials, information, building or design help). Companies that give great customer service, have loyal customers that spread the word every chance they get! Recommendations from people we know carry a lot of weight.

A simple move of a thermostat, or (fairly) simple re-zoning of the fossil/electric heating system, could greatly improve the user experience... the same RMH being no longer "to blame" for chilly rooms. Now, the story is about how wonderful the bench is, and how they never want to leave it, because it is so cozy (NOT because they dread the cold bedroom down the hall). They'd probably use the RMH even more often, since it'd never be so cold that they felt they needed to give in and just use the furnace instead.

Julie Reed wrote:
Most woodstoves are at least 50% efficient, so logically the most you could possibly improve on that would be to 100%, or half the wood, not 1/10th. My backyard is many acres, so I suppose I could maybe heat with all my twigs, but overall that's unrealistic for the average homeowner. Heating a house needs a certain number of BTUs regardless of where they come from. In cold areas, the minimum is probably going to be a full cord of wood, depending on many other factors like size of dwelling and weatherization. I recently spoke with a couple who just added an RMH to their fairly new (thus energy efficient) 1200 sf home in 2020, when they had free time due to covid shutdowns. The style is ranch, with a rectangular layout of 30x40. Their RMH is centrally located, and yet even with fans they cannot get adequate heat to the rooms on the ends during '20-30 below' nights (which there are many of, for anyone in northern states...

First off, thanks for sharing your friends experiences! The more solid examples we have the easier it is to get a sense of how they work.

I want to try to take a crack at the 1/10th the wood thing, because I have never heard a clear explanation of it, and it was mindblowing when I thought about it.
A regular stove is 50-80% efficient. You will hear disputes on whether the certification figures reflect the real world usage. They probably don’t, but this is small potatoes. The real question is, what is that number referring to?
The answer is that it is measuring the percentage of energy in the wood that is converted into heat. This is NOT the same as the heat that is dumped into your home, because plenty is carried out with the flue gasses. How much is a number I have trouble finding, but I think that upon exiting the building, flue gasses from a standard stove are something like 300-900 degrees, while the fire should be 500-1100 degrees to avoid warping the iron. So you are losing quite a lot if heat out the chimney: I am not sure how to calculate the percentage of total heat produced without knowing what the airflow is. In comparison, a masonary stove or an rmh are supposed to reach more like 2000 degrees in the firebox, and the flue gas should be less than 200. So 90% of the heat liberated from the wood stays in the mass, to be radiated into your home.
So, 1/10th the wood may not be as far off as it seems at first.

Anne Miller wrote:Now we are getting somewhere:

Lina said, "It is the mass - the large bench, and all the cob surrounding it the barrel- that is so heavy.

Do all RMH use cob?

Well, there is the pebble style, which uses pebbles instead. There are masonary heaters which use rock and brick. Probably some rmh which do so too.
The point is that you need a material dense enough to pull 90% of the heat out of the fire and release it over several days. In order to do that, it has to be heavy. Anything light will insulate the pipes, making them carry heat out of your house instead of storing it.
You can have a rocket heater, without the mass. I use one in a tiny house I built on my parents land. It heats up fast with twigs and scraps and has a nice clean burn. But it gets cold as soon as it goes out, meaning you run it constantly whenever you want heat. It gets frosty in there at night… noy what you want when trying to heat a whole house, and not much better than a modern wood stove.

Lina Joana wrote:
I want to try to take a crack at the 1/10th the wood thing, because I have never heard a clear explanation of it, and it was mindblowing when I thought about it.
A regular stove is 50-80% efficient. You will hear disputes on whether the certification figures reflect the real world usage. They probably don’t, but this is small potatoes. The real question is, what is that number referring to?
The answer is that it is measuring the percentage of energy in the wood that is converted into heat. This is NOT the same as the heat that is dumped into your home, because plenty is carried out with the flue gasses. How much is a number I have trouble finding, but I think that upon exiting the building, flue gasses from a standard stove are something like 300-900 degrees, while the fire should be 500-1100 degrees to avoid warping the iron. So you are losing quite a lot if heat out the chimney: I am not sure how to calculate the percentage of total heat produced without knowing what the airflow is. In comparison, a masonary stove or an rmh are supposed to reach more like 2000 degrees in the firebox, and the flue gas should be less than 200. So 90% of the heat liberated from the wood stays in the mass, to be radiated into your home.
So, 1/10th the wood may not be as far off as it seems at first.

Have you seen this video? Watched it last week, and it touches on some of the points you make. Found it really fascinating!

I had clicked the "Buy Now" button. Didn't realize the red dollar amounts were links. Tnx.

Jimothy J

Christine Circe wrote:

Jimothy Jimson wrote:Perhaps it is just on my end. Ida know. Will try again later.
Tnx,
Jimothy J

Margaux Knox wrote:

Beau Davidson wrote:

Jimothy Jimson wrote:


That's weird, all 4 links work for me, loading up with the correct amount in a paypal checkout window.  

Anyone else having trouble with the payment links at https://richsoil.com/wood-heat.jsp?

Works for me!

Hi Jimothy,
It looks like the yellow buy here button is inopt. Can you tell me if you've clicked on the red hyperlinked dollar amount of the one you'd like to purchase?

I will attach a screen shot for reference.

The video tends to skew things in favor of the rmh by stating things like "if you put a green log on the fire to smolder all night". Well, yeah, if you burn green wood in an RMH it's not going to do as well either. Based on 'all other things being equal', if both heaters use wood dried to less than 20% moisture content, and we determine how many BTUs are in a cord of hardwood, then we start getting better numbers. I realize that some of the heat from a woodstove goes up the pipe. However, my understanding is- that is factored into the efficiency rating. Thus the 50-70% is actual realized heat from the wood burned. Do woodstove companies play games with numbers? Probably. But their reputation and success rests on selling quality stoves that do what they are supposed to do. The folks I mentioned in my previous comment went from a secondary burn high efficiency woodstove to an RMH, and said they were still burning more than half of their previous consumption. Just one example but...

Julie Reed wrote: I realize that some of the heat from a woodstove goes up the pipe. However, my understanding is- that is factored into the efficiency rating. Thus the 50-70% is actual realized heat from the wood burned

Huh - that was not my understanding, but I may be totally off base. Do you have a source with a good description of how they do the tests for stove efficiency?
Your friend’s experience is compelling- it may be that the 1/10 number does come from people not using their stoves properly - it is easier to toss big logs in that will smolder, green or not, and harder to maintain a clean burn.

These questions are addresed in the short videos and various other places.
The best commercial devices are rated under ideal conditions. In practice they perform much lower (less than 50%) and have a bonus allowance for heat created but lost up the flu (16%?) So a careful operator might expect 35%. Careless 20% efficiency.
RMH beats all of these. And because of the fuel used is more likely idiot proof (likely to perform at the higher end).

Julie Reed wrote:The video tends to skew things in favor of the rmh by stating things like "if you put a green log on the fire to smolder all night". Well, yeah, if you burn green wood in an RMH it's not going to do as well either. Based on 'all other things being equal', if both heaters use wood dried to less than 20% moisture content, and we determine how many BTUs are in a cord of hardwood, then we start getting better numbers. I realize that some of the heat from a woodstove goes up the pipe. However, my understanding is- that is factored into the efficiency rating. Thus the 50-70% is actual realized heat from the wood burned. Do woodstove companies play games with numbers? Probably. But their reputation and success rests on selling quality stoves that do what they are supposed to do. The folks I mentioned in my previous comment went from a secondary burn high efficiency woodstove to an RMH, and said they were still burning more than half of their previous consumption. Just one example but...

That's not making sense to me Steven. Where is the heat going? You start with a piece of firewood that ends up ashes. That's 100% combustion (heat). If the stove is only 50% efficient, then that means half the heat went up the chimney. It also means half the heat stayed in the house. But then you are adding in more percentages of inefficiency. Where is that heat being lost? I think you are double counting the heat lost up the stack, but maybe I'm not clear on the explanation. The bonus allowance of 16% is what makes the initial rating higher than 50%, no? What I was told by Vermont Castings years ago was the rating is based on BTUs contained in X amount of wood, versus BTUs radiated into the heated space when that wood is burned. And yes, they do the rating when the stove is up to temperature, not while starting a new fire. So if you let it burn out and start new fires every day, instead of filling every 8-10 hours to keep a constant fire, you'd lose points there.
I'm also not clear on what you mean by "RMH beats all of these. And because of the fuel used is more likely idiot proof". What fuel is used in RMH that's different than a woodstove?

The fuel is small pieces, not large lumps. The burn chamber is optimized , as is the secondary combustion. It's not surprising your friends achieved less than 90% gain moving from a secondary burn heater to RMH because that technically is already halfway there. No burn is 100%- there's ash, charcoal, Co2 etc as byproducts.
RMH attempts to capture more of the heat using the Mass; extra long horizontal flu and absorbing surround. The only thing more efficient is Nuclear reaction .

Julie Reed wrote:That's not making sense to me Steven. Where is the heat going? You start with a piece of firewood that ends up ashes. That's 100% combustion (heat). If the stove is only 50% efficient, then that means half the heat went up the chimney. It also means half the heat stayed in the house. But then you are adding in more percentages of inefficiency. Where is that heat being lost? I think you are double counting the heat lost up the stack, but maybe I'm not clear on the explanation. The bonus allowance of 16% is what makes the initial rating higher than 50%, no? What I was told by Vermont Castings years ago was the rating is based on BTUs contained in X amount of wood, versus BTUs radiated into the heated space when that wood is burned. And yes, they do the rating when the stove is up to temperature, not while starting a new fire. So if you let it burn out and start new fires every day, instead of filling every 8-10 hours to keep a constant fire, you'd lose points there.
I'm also not clear on what you mean by "RMH beats all of these. And because of the fuel used is more likely idiot proof". What fuel is used in RMH that's different than a woodstove?

Lina said- "Your friend’s experience is compelling- it may be that the 1/10 number does come from people not using their stoves properly - it is easier to toss big logs in that will smolder, green or not, and harder to maintain a clean burn."

You can't blame poor efficiency on the stove, if people are using it improperly. That would be like saying X brand cars claim 30 mpg, but only get 14 mpg, but it's really because the drivers are riding the brake pedal.
That's my issue with the video, it's listing every possible misuse of the woodstove and then using that situation as a basis of comparison. What about if the woodstove is used correctly and burning bone dry wood? Because that's the standard held for the RMH, right? I don't dispute for a minute that the RMH is obviously more efficient and cleaner burning. But I also think you'd have to make deliberate mistakes to get less than 50% out of a good woodstove.
We heat 1800 sqft on about 2 cords a year with a very efficient stove. There is no way we could heat all winter on 1/5 of a cord (1 tenth of 2 cords)!

Steven wrote:The fuel is small pieces, not large lumps. The burn chamber is optimized , as is the secondary combustion. It's not surprising your friends achieved less than 90% gain moving from a secondary burn heater to RMH because that technically is already halfway there. No burn is 100%- there's ash, charcoal, Co2 etc as byproducts.
RMH attempts to capture more of the heat using the Mass; extra long horizontal flu and absorbing surround. The only thing more efficient is Nuclear reaction .

Not everyone burns 'large lumps' (we split everything to about 4-5" so a piece can easily be picked up by the end with one hand) but I agree that larger wood is less efficient, though to what % I'm not sure.  Tossed in to a hot firebox full of coals it's likely not much. All woodstoves sold in the last 30+ years are epa rated, meaning either a secondary burn or a catalytic burn. That's where the ~70% number comes from. I guess if you are comparing an RMH to an old potbelly or Franklin stove then it would be far more efficient. Co2 should be mostly vaporized in the burn chamber once any stove is up to temperature. We never have charcoal, but 2 cords of wood produces about 20 gallons of ashes.
I'm not in any way disputing the high efficiency of an RMH, just the mis-characterization of woodstoves. There is no way we could heat on 1/10th of 2 cords for 6 months of winter. That's simply not enough BTUs to keep 14,000 cubic feet of house warm. Even 2 cords is low, but we have good southern exposure and solar gain, except for mid November to mid February.

I agree that the "1/10" figure is not relevant to a modern woodstove operated wisely. The best of them may be at least half as efficient as an RMH overall, leaving only marginal room for improvement. But most woodstoves are not the best, and except in large houses where a huge stove is required and thus a large amount of wood can be loaded at once, cannot be burned efficiently overnight but must be damped down to last til morning, or damped down in milder weather to provide constant heat without baking the occupants or forcing windows to be opened.

A woodstove burns most efficiently at one heat delivery rate or a fairly  narrow range. An RMH can always be burned at top efficiency, and burned longer or shorter to provide the day's even heat as required.

I burn about one cord of wood a year, and when I measured it (keeping all the ashes), I got about 5 gallons of ash for the year. There is absolutely nothing but mineral ash left.

By the way, CO2 and H2O are the essential products of perfect combustion. Carbon monoxide is produced (and not consumed) in incomplete combustion, along with creosote and coals left unburned.

Julie Reed wrote:

Lina said- "Your friend’s experience is compelling- it may be that the 1/10 number does come from people not using their stoves properly - it is easier to toss big logs in that will smolder, green or not, and harder to maintain a clean burn."

You can't blame poor efficiency on the stove, if people are using it improperly. That would be like saying X brand cars claim 30 mpg, but only get 14 mpg, but it's really because the drivers are riding the brake pedal.

Oh, I agree!
So maybe, bringing this thread back to the question of “what is keeping people from getting excited about the concept and sharing it with others to make it go viral”:
1) some of the info out there seems to good to be true, and at least some people have found it to be so - an rmh uses half the wood of a properly used super efficient wood stove, not one 10th, at least in some houses.
2) The downsides to implementation are - may need to remodel your house to take the weight, you need much thinner pieces of wood to fit in the jtube (more time splitting), and you need to spend several hours constantly feeding it during the burn.
3) There are regulatory barriers, and the fact that there isn’t an obvious path through those makes it seem like a risky and experimental technology- not what you would encourage your neighbor with an old furnace to install.

In sum, if people don’t feel comfortable sharing it because they aren’t sure its real, it will not go viral.

Unfortunately, it will most likely take time. More heaters are getting installed each day, which means more people will see them. Eventually, there will be enough around that pros will feel comfortable building and even recommending them. But I don’t know how to speed that up.

One issue, that wood needs to be split tiny (= lots of extra work) is not really true. You can't use huge hunks of log, but once the fire is burning, you can use logs of a size to only fit a few - or up to 4-5" across for an 8" J-tube or even a bit larger for a batch box. You can also reasonably use branch wood or other things that are already too small to be practical in a box stove and require only cutting to length and no splitting.

A major reason for splitting wood smaller aside from fitting is that thinner pieces dry faster and more thoroughly. Much delivered firewood at least in upstate NY is barely seasoned or has been seasoning outside in heaps and is not really dry. If bought in late summer or fall for the following winter, large logs will still be damp when put in the stove. I know this is not good practice, but it happens often.

Hard to find a more complete, consice, and direct answer to almost all of these questions than this:

https://richsoil.com/wood-heat.jsp#faq

The Rich soil faq is fine. To anyone stumbling on it, it is a random web page that is throwing out numbers that don’t sound believable, with no references to back them up.
Take the answer to the “10 times more efficient” question. Ok, so the 75%+ efficiencies come from optimum lab conditions. But where do the rest of the numbers come from? Who has established that a really good operator who is burning dry wood can only get 35%? How do we know that “most” people use their wood stoves at 3-15% efficiencies? The 1/10th numbers come from “people we know”… who are these people, and what kind of stoves were they using? Did they actually know how to use them? Why should I give any credence to the people some guy on the internet knows?
Finally, these questions keep coming up because the experiences are not universal. There has been mention on this thread of the couple who is using around half the wood they used to. Nice savings, but not even close to 1/10th, and doesn’t heat the far out rooms. So there is a lot of conflicting information (all of which is actually true, depending on the situation) and it all starts to sound like hype.

The statement that RMHs use 1/10th the wood of a conventional wood stove is where you continue to lose me. We heat a 2400 sq. ft. home using a conventional wood stove, use 1.5 cords of wood a year, and we're in northern Idaho zone 6a. It gets cold. I believe I saw in a post that Paul uses 0.6 cords of wood a year.

Now we do know many people that use 6 cords of wood a year, so in some cases the 1/10th value works, but there are so many details and variables that aren't spelled out like square footage of the home, insulation of the structure, etc. to make a solid comparison. I think the best comparison would be the same structure using a conventional stove then retrofitted with a RMH with no other changes. That would be some great information to show the efficiency increase with a RMH.

As Robin points out, there are so many variables not only with the property but the stove itself …. A basic J tube with little or no insulation or a precision  batchbox, made largely from insulating materials ….  Bicycle v car!
Some units are going to perform much better than others and some houses will hold heat better than others.

This is the most interesting thread I have ever read on permies.  Even though I live in northern Florida, I am considering one of these.  My question is though: Do you need the bench to be so big or can it be small as the size of some of these benches would take up too much of the living space.  Is there a way for these benches to go vertical?

Kate Callahan wrote:This is the most interesting thread I have ever read on permies.  Even though I live in northern Florida, I am considering one of these.  My question is though: Do you need the bench to be so big or can it be small as the size of some of these benches would take up too much of the living space.  Is there a way for these benches to go vertical?

The bench can be BIG!

The bench can be  small.

The bench can be   W    I     D     E

  T
  A
  L
  L

I'll just describe my difficulties in promoting the RMH:

I myself have known about the RMH for two years now. Even before the catastrophic energy crisis in Germany, I had sought for a solution in my basement rental appartment without chimney (electrical storage heating). I can't do it myself (I am an economist and all thumbs).

I have seen a huge amount of youtube-videos, have read blog posts and forum articles. I have no problem with ALL of it being in English.

Now I have a friend who is a chimney sweep. In Germany, this is a professional who not only cleans and supervises all burning facilities in homes (oil, gas, wood, ...), but also has to check emissions and also does the legal acceptance (is that the right word?) for any fireplace in buildings. Like an electrician who has to confirm the installation before you are allowed to turn the switch, the chimney sweep has to come and check and approve your stove/chimney etc. before you put it into operation.

He would be someone who has knowledge and also is essentially necessary to convince, if I would want to install a RMH.

Now I tried to find information for him - he does not speak very much English. There is almost no material in German. Also, the copious videos from Paul Wheaton's RMH gang are showing lengthy discussions, experiments and variations, but what I need is one video with all the 2022 knowledge (not: how did we do it three years ago until we came up with a better solution) in a nutshell. This is why I contributed to the kickstarter. But I'm afraid it will again be all in English.

So: I need a good synopsis including building information for people who already have knowledge in conventional wood heating, and at least with German subtitles; forget about automatic captions. Even better an internet site with an introduction (more than https://www.youtube.com/watch?v=fwCz8Ris79g) and then information in detail. Heaven would be: some legal information for EU-residents.

Similar to people in the US, who can tell their authorities: Hey, in Portland, this already has a building code!

If I could get the message to my friend the chimney sweep and he would approve of the concept, I could persuade my landlord and find some builder to build it for me. But the legal "go" is mandatorily the first step.

Thank you Christine!!

Yes!  Here in the United States it is easy for us to forget that not everyone in the world speaks English!  Thanks for reminding us!  I will look into this and see what I can do.

Eric

OK, Christine makes a really great point.  Germany has a real need for RMH’s right NOW!  It’s going to start getting very cold very soon so anything we can do to spread the word would be really advantageous.

Are there any German speakers who would be willing to donate a little time to add subtitles to a video?  I am totally thinking on my feet here and I don’t know exactly how we connect A to B, but getting some German subtitles sounds like a great suggestion.

Eric

Christine Schwabe wrote:Now I tried to find information for him - he does not speak very much English. There is almost no material in German. Also, the copious videos from Paul Wheaton's RMH gang are showing lengthy discussions, experiments and variations, but what I need is one video with all the 2022 knowledge (not: how did we do it three years ago until we came up with a better solution) in a nutshell. This is why I contributed to the kickstarter. But I'm afraid it will again be all in English.

So: I need a good synopsis including building information for people who already have knowledge in conventional wood heating, and at least with German subtitles; forget about automatic captions. Even better an internet site with an introduction (more than https://www.youtube.com/watch?v=fwCz8Ris79g) and then information in detail. Heaven would be: some legal information for EU-residents.

I don't know or understand German.

I also understand you want the latest information for 2022.

I was wondering if either of these would help explain to your friend even though they are not 2022:





One thing I have learned from reading the forums is to call the RMH a Masonry Stove.  It seems that more people understand what a Masonry Stove is.

Here are some threads that you or others might find helpful:

https://permies.com/t/189383/Rocket-Mass-Heater-design-fits
https://permies.com/t/19210/RMH-Germany
https://permies.com/t/28151/mass-heater-Germany-Deutschland

Also you might try to contact the people at the link found here:

https://permies.com/t/28021/Workshop-Germany-Sept

You also might contact these members by PM (Purple Moosage) as they might be able to point you in the right direction:

https://permies.com/u/152487/Peter-van-den-Berg

https://permies.com/u/95396/Satamax-Antone

Anne Miller wrote:

I was wondering if either of these would help explain to your friend even though they are not 2022:

Anne, thank you for your suggestions! Some of the videos I already knew. The problem is: They are all marketed/allowed for outdoor use only. The threads from the forum are 8 respective 9 years old, forgive me that I won't revive these.

I would really like to have an explanation of the basic principles of the J-tube and the barrel (all the physics to it), why does it burn so clean, why does the fire burn sideways, what happens to the heat when it hits the heat riser's top and so on ...
And also info about topics like
* cleaning
* material of the heat riser (I am aware that there is a video on it, but it is a quite lengthy discussion, was okay for me, but not for inspiring others)
* questions about wall insulation, how to prevent mold
* static concerns
* how high does the flue need to be etc.