are rocket mass heaters "appropriate technology" given the availability of efficient woodstoves?

Davis Tyler wrote: Unfortunately I don't think any of the mass designs would work for a retrofit in existing homes around here.  We all have basements, and there's no way standard flooring would support the additional several thousand pounds of cob or masonry it wasn't designed for.

I have one in the house I am in right now.  A double wide.   We added support from below.  Not that big of a deal.  

Davis Tyler wrote:I think that was the very first RMH video I watched!  Got me interested in understanding the tech behind it.  So, OK 1/2 a cord of wood for a garage on the Pacific coast is not that impressive.  I have a 2400 square foot home I'm heating in NH when I talk about 3-5 cords.  It routinely hits -10F here, sometimes -20F.  It would be interesting to see how they fare with heating an entire home in their new location

That particular video is from the okanogan highlands.  No where near the coast.  In the video it shows that there has been snow on the ground for months.  Their weather happens to be the sort that they usually don't get a break from the snow all winter.  And I am not certain, but I suspect it gets colder there than it does at your place.

We must have different tastes.  Two of those have some nice tile/stonework, the others...and the 50-gallon oil drum in my living room ain't happening.  What happens if you've covered the barrel in beautiful stonework and later you need to clean/repair/replace it?

The bell designs in general don't have a barrel at all. Aside from the necessary mass/bulk and the fire access, you can make your RMH look like whatever you want.

I have built a metal access panel into the side of my RMH bell so that I have complete access for maintenance and repair if ever needed; it also gives some of the "instant radiator" effect the barrel (or a woodstove) usually provides.

We've had some cold weather the last couple of weeks.   A hard frost a few days ago.   We haven't lit a fire yet this year although the day for the first fire is coming soon.    Outdoor highs have been in the 60s.  Lows in the 30s or 40s.  

We leave several windows open a little bit.   I just like it that way.  

Indoor temps have been around 68 to 70.   I think it is the mass keeping us this warm.   The two of us do work from home, so our bodies and laptops are putting off some heat.  There is some cooking.   We did have a dozen people over for dinner a couple nights ago.  I think that without the mass the house would have gotten too warm and we would have needed to open some windows.   Instead, the interior was always comfortable.   I think that this is not 100% the doing of the mass, but I think it might be as much as 85%.  

You definitely notice it on hot day.  You come inside and it is MUCH cooler inside.  And I think it is largely because of the mass.

Davis Tyler wrote:We must have different tastes.  Two of those have some nice tile/stonework, the others...and the 50-gallon oil drum in my living room ain't happening.  What happens if you've covered the barrel in beautiful stonework and later you need to clean/repair/replace it?

It is important to not cover the barrel (or fabricated bell) with anything.   The barrel needs to not only give off heat, but the interior gases need to dramatically cool at this point.  That is the secondary thermosiphon.

Davis Tyler wrote:We must have different tastes.

There have been thousands of these built.  Different folks can all share their different ideas.   This entire field is just getting started.   While there are currently books and plans for all sorts of different rocket mass heaters so far, I suspect that one day there will be books of 300 different rocket mass heater designs - just like you can find for a log cabin or any style of house.

I've gotta see a picture of this RMH in a double-wide!

Davis Tyler wrote:I've gotta see a picture of this RMH in a double-wide!

You can see the whole build in DVD 2 of Better Wood Heat: DIY Rocket Mass Heaters.  We call this house "the fisher price house."

Here is a still from dvd 2 - that's me sitting on it explaining the work done.

I have been lurking here in the forums for a long time and seen your praises for rocket mass heaters..and you hope for more thermal mass.
In our country we have been using same design, basically, for at least couple hundred years. Only difference i see in design that rocket mass heater gives most of the heat instantly.

We call these by the name: pönttöuuni

Idea behind this is the same, except that pönttöuuni gives heat for one day with couple loads..
Here is the google link for some images: http://www.ponttouunit.com/ponttouunit/kuvagalleria-uunit/

I now have the following rocket mass heaters:

1) fisher price house (pebble style, ceramic fiber core)
2) office (pebble style, wood box core)
3) shop (brick batch box and pebble style)
4) ring of fire (outdoors)
5) smoker and butt warmer (outdoors)
6) red cabin (minnie mouse design)
7) love shack (waterbug not yet installed)
tipi (cob style, wood box core)
9) cooper cabin (cob style)
10) allerton abbey (batch box, massless heater)
12) garage (fat rabbit not yet installed)

There is also the indoor rocket cook stove at cooper cabin, and the indoor rocket cook stove that erica built that needs a home.  Maybe allerton abbey.  And we have the rocket kiln that ernie built.  That's all I can think of right now.

I grew up with wood stoves and have used a LOT of wood stoves over the years.   I have fed a LOT of wood to all sorts of different wood stoves.   I have seen people build all sorts of custom stoves and my last conventional wood stove had some fancy pipes on the inside to improve the burn.   I cannot even imagine going back to a conventional wood stove.   What a lot of extra work.  And they are so dirty.   On days where we don't fire up a rocket mass heater, we can smell the smoke of the neighbors.   And when we do burn, most of the burns are just steam coming out the top.    Especially the rocket mass heater in the fisher price house.

If somebody offered me a $10,000 conventional wood stove for free to replace any of our rocket mass heaters, I would turn it down.  I cannot help but think that it would eat ten times more wood and you still wouldn't be as comfortable.  

With a rocket mass heater I am far more comfortable and I burn far less wood.  

Here is a thread from over a year ago called "science and lab results to support the claims behind rocket mass heater":  

https://permies.com/t/44669/rocket-mass-heaters/science-lab-results-support-claims



Here is "why the rocket stove works so efficiently":

https://permies.com/t/55938/rocket-mass-heaters/rocket-stove-works-efficiently



Erica put together a rather thorough FAQ:

https://permies.com/t/41635/rocket-mass-heaters/Top-Questions-Rocket-Mass-Heaters

Currently, most people report that when they switch from a conventional wood stove to a rocket mass heater, they reduce their wood use by 80% to 90%.   And they are more comfortable.  More comfort and much less wood.  

If we can get ten times more people heating with rocket mass heaters, I think we might continue to improve these systems so that we can reduce wood use by 95% to 96%.    This would be things that involve the ceramic fiber cores, something automated to shut off the exhaust, something automated to bypass the exhaust through the mass, something automated for closing the intake ...  I have also been thinking a lot about reducing the overall size of the exhaust duct.  I also think there could be some new stuff with stratification chambers within the mass.  And I also like the new direction we are seeing with indoor rocket cook stoves.  

Not only are rocket mass heaters currently far superior to the best conventional wood stoves available, but I think we are just getting started.  

paul wheaton wrote:

Davis Tyler wrote:I think that was the very first RMH video I watched!  Got me interested in understanding the tech behind it.  So, OK 1/2 a cord of wood for a garage on the Pacific coast is not that impressive.  I have a 2400 square foot home I'm heating in NH when I talk about 3-5 cords.  It routinely hits -10F here, sometimes -20F.  It would be interesting to see how they fare with heating an entire home in their new location

That particular video is from the okanogan highlands.  No where near the coast.  In the video it shows that there has been snow on the ground for months.  Their weather happens to be the sort that they usually don't get a break from the snow all winter.  And I am not certain, but I suspect it gets colder there than it does at your place.

Just Googled the location - sounds like very similar heating requirements to my location 7200 vs. 7400 heating degree days.  Found this nifty resource for others interested in comparing the heating and cooling requirments of various locations:  https://www.huduser.gov/resources/utilitymodel/source/select_Geography.odb

thanks for the links; I'll keep reading

I see a lot of tinkering and R&D, which is great, but I haven't seen a lot of maturity in a "best practices" type of design.  

I see oodles of maturity and excellent design.  I guess our experiences are radically different.

Aesthetics are certainly in the eye of the beholder, but if I tried to bring a 50-gallon steel barrel and cob into my living room, my wife would have me sleeping outside with the dog  

If you are gonna do new stuff, it is gonna look different.  

If the issue is the barrel, a lot of people go with a fabricated bell.

I see a lot of people burning up and corroding metal burn tubes, sending lots of toxic gick into the atmosphere.  It sounds like most folks have now seen the light in using refractory materials.  

It was about five years ago we ditched metal in the core.

I see people experiencing puff-back of smoke into their living space

I have less smoke getting out than I used to have with my conventional "efficient wood stove."

....  $900 and burns at ~70% efficiency.

I would like to suggest that you book up on what that "70%" means.   First, "70%" actually means "54%" because 16% is allowed to go up the chimney.  Second, they got to 54% on just one burn out of dozens.  Did they kiln dry their wood for the test?  Did they artificially increase the air pressure in the lab - which then blows air on the wood during the burn?   Did they use a variety of wood that has an especially high BTU?  What other factors did they fiddle with?  

When the average person runs that same stove in their home, are they running it at 8% efficiency?  3% efficiency?    And what sort of results would that average person get with a rocket mass heater?  80%?  85%?

How long would it take you to gather 3500 lbs of twigs and sticks to feed your RMH?  

What does that have to do with anything.  

Are you suggesting that people running rocket mass heaters are required to only burn twigs and sticks?   I am currently using mostly split firewood, just like I would with a conventional wood stove.   And when i would burn with a conventional wood stove, I would burn twigs and sticks too - better than throwing them away and gathering cordwood.  

I understand that some extremely poor people do not have the means to buy an EPA woodstove.  I understand the appeal of a RMH in an outdoor application like heating a greenhouse where a design mistake doesn't lead to catastrophic loss of life.  But I can't understand why anyone with a better alternative would take the risk of building one of these things in their house.  What am I missing

I am utterly confused at this.  

I think that the part about catastrophic loss of life is entirely on the part of conventional wood stoves.   Chimney fires top the list.   And all of the dangers of any kind of wood heat will be ten times greater with a conventional wood stove because the conventional wood stove uses ten times more wood.  Ten times more chance of burns and ten times more chance of some sort of CO2 problems.   In fact, for a batch box system here, the burn was measured and for 3/4 of the burn there was ZERO CO.  ZERO!   Where on earth are you finding this bizarre misinformation?

That is slow and low.  

Compared to a rocket mass heater which only does hot or zero.   Most of the time, there is no fire at all, and it is still pouring heat into the room.

1/2 to 1/8 wood consumption is a remarkable claim.

I don't know where you found that claim.   The claim is 1/5 to 1/10.  And that's for rocket mass heaters of today.   I like to think that in the next few years we can take that up to 1/20.

paul wheaton wrote:

I understand that some extremely poor people do not have the means to buy an EPA woodstove.  I understand the appeal of a RMH in an outdoor application like heating a greenhouse where a design mistake doesn't lead to catastrophic loss of life.  But I can't understand why anyone with a better alternative would take the risk of building one of these things in their house.  What am I missing

I am utterly confused at this.  

I think that the part about catastrophic loss of life is entirely on the part of conventional wood stoves.   Chimney fires top the list.   And all of the dangers of any kind of wood heat will be ten times greater with a conventional wood stove because the conventional wood stove uses ten times more wood.  Ten times more chance of burns and ten times more chance of some sort of CO2 problems.   In fact, for a batch box system here, the burn was measured and for 3/4 of the burn there was ZERO CO.  ZERO!   Where on earth are you finding this bizarre misinformation?

The first thing I saw when I logged in this morning is some guy who set his floor on fire: https://permies.com/t/39987/rocket-mass-heaters/Rocket-Mass-Heater-success-Saskatchewan

Chimney fires are mostly caused by people burning unseasoned "green" wood.  It's really not fair to blame the appliance

My thoughts are that those able to purchase a UL/EPA-certified woodstove are unwise to be tinkering with homemade rocket heater designs that could potentially burn down their home or CO-poison the occupants.

DA-FUCK?

How is anybody getting poisoned?    Are you trying to run a rocket stove (which is NOT a rocket mass heater, a rocket stove is a type of outdoor camp stove) inside your house?  

Here is a tip:  compare a conventional wood stove, designed for heating the interior of a home and shoots its smoke outside, with a rocket mass heater, which is also designed for heating the interior of a home and shoots its exhaust outside.  

I think that those that are able to purchase a $5000 wood stove would be much happier shelling out $2000 to have somebody build them a rocket mass heater.

I wrote "1/2 to 1/8" earlier here as a very modest claim, as I recall one thread mentioning half as much wood use as before. I wanted to forestall the attack of "somebody didn't get 1/4, they only got 1/2".

paul wheaton wrote:
I think that those that are able to purchase a $5000 wood stove would be much happier shelling out $2000 to have somebody build them a rocket mass heater.

Is that an option, today?  I skimmed through some discussions on building codes and home insurance etc. but didn't really come to a conclusion if it was legal to build one of these in most states?

The guy who charred his floor was warned before he used it that his system was seriously flawed. He used it anyway, while keeping somewhat of an eye on it, and learned his hard lesson easier than he might have.

RMHs should be permittable as masonry heaters in jurisdictions that have a halfway sympathetic official. The one serious official difficulty is that by code a masonry heater has to be built by a recognized professional.

Given the vertical orientation of a typical masonry heater, with its concentrated floor load and possibility of tipping over in earthquakes, as well as the complicated contraflow flue path, this makes sense for the typical masonry heater.

Davis Tyler wrote:
The first thing I saw when I logged in this morning is some guy who set his floor on fire: https://permies.com/t/39987/rocket-mass-heaters/Rocket-Mass-Heater-success-Saskatchewan

Chimney fires are mostly caused by people burning unseasoned "green" wood.  It's really not fair to blame the appliance

HA HA HA HA HA HA HA HA HA HA HA HA HA HA HA HA HA HA!

Sorry, man .... okay, ha ha ha .... okay ...   so .... ha ha ....  you are saying that ....  ha ha ....   it's totally cool for somebody to burn their house down and kill all of their family with a conventional wood stove, but if somebody skips a step on a rocket mass heater and it gets warm, but nobody gets hurt, that's dangerous?

So, just a few months ago Erica came out with her rather excellent book:



link

So after ten years of people making poor choices, we have a really excellent book.   Of course, we have all the plans and stuff the erica has put out the last couple of years too.   And the videos can be of some help.  But, the fact that a lot of people were looking at scary youtube videos and some dodgy web pages ....  we can finally put all that behind us.   Further, don't forget to go find all the conventional wood stove disasters out there too.   including the store bought conventional wood stoves that were installed in an "interesting" way.

Glenn Herbert wrote:I wrote "1/2 to 1/8" earlier here as a very modest claim, as I recall one thread mentioning half as much wood use as before. I wanted to forestall the attack of "somebody didn't get 1/4, they only got 1/2".

Fair enough glenn.  

The weakest I have heard to date is "1/4".   I have heard of a few people doing better than "1/10th".  But it seems that most people are getting around "1/5" to "1/10".  

So, if I'm gonna have the conversation, I will gladly use "1/4 to 1/10th the wood" and stand by it.   but that's just me.  

Davis Tyler wrote:

paul wheaton wrote:
I think that those that are able to purchase a $5000 wood stove would be much happier shelling out $2000 to have somebody build them a rocket mass heater.

Is that an option, today?  I skimmed through some discussions on building codes and home insurance etc. but didn't really come to a conclusion if it was legal to build one of these in most states?

I have heard of people building them for others in exchange for monies.   I know that Ernie and Erica will lead a workshop build for folks.  

Building codes in portland definitely know about home-built rocket mass heaters and I think a lot of other places are including it too.   That's kinda  the thing about innovation:   it's against the law until it isn't.   Somebody has to push that boundary until the laws are upgraded.  

Currently, it is legal to build a rocket mass heater outdoors anywhere in the US.   And then there are a lot of places where it is legal indoors - like where I sit.  And then there are people that are building them in areas where it is not legal - that is their decision.  

I like to think that in a few years it will be universally legal.  And there might even be a government subsidy to build one.

"1/4 to 1/10"

That's what I generally use in conversation too

Just a quick and I hope relevant question , these super new fires with the platinum catalyst that needs to be changed ever five years ( I have not  seen any here in France ) how much do they cost to replace the catalyst ? not the environmental cost but the actual $$$$ or how much does that add to your bills per week weather you use the fire or not or even in term of wood saved ?

David

I tend to think longer term and my philosophy is to buy the highest quality tool for the job to decrease the maintenance and replacement cost over time.  As I mentioned a cast iron woodstove will last for decades with minimal maintenance.  

The oldest rocket mass heater is now 20 years old and is showing no sign of becoming sad.  

The best tool is, hands down, the rocket mass heater.  No contest.    A $500 rocket mass heater is three times better than a $5000 conventional wood stove.  

Compared to your best conventional wood stove, a rocket mass heater is downright luxuriant.  The conventional wood stove is for the "poor people" you speak of.   The ignorant masses that have not yet learned about rocket mass heaters.  

Hi everybody.

Well Davis, the stoves with catalyst you are talking about range from 70 to 80% burn efficiency, in the ideal conditions. If smoldering, even with platinum foam catalyst, they do a good 40 to 50 may be. After, all the numbers are advertising.

And this is just burning efficiency. Not heat recovery. A finely tuned rocket mass heater can run with chimney temps of about 80C° Even down to 60C° for some. But that's tickling the dragon's nose.

You realise that is from a fire, in excess of 1200C° So 1200-80 = 1120C° left in the stove. Well, it doesn't exactly work like this. Since hot gases expand, there's more chimney gases than intake gases. There's evaporation or supersaturating of air and wood moisture.

But a good RMH can reach 85% burn and recovery efficiency. There's is no challenger, besides mass heaters. No metal wood stove will reach this total efficiency. May be some pellet condensation boilers. But, they are mass heaters. And pellets can't be called wood anymore.

A well tuned Peter van den Berg J tube, can reach 95% burn efficiency at the peak of the burn, IIRC. Tho, startup and ember stage drag those numbers down.

I think, regarding those numbers, RHM are appropriate technology. And for the poorer people, who can't afford a state of the art modern "commercial" wood stove.  It represent a really interesting alternative. You see, i insist on commercial. There's corporations making money on the commercially available box stoves. Not philanthropists. So, when you read their numbers, take them with a grain of salt.

Poor people are not necessarily dumb either. And with careful planning, good scavenging methods, they can obtain the right materials for cheap. Still not a viable alternative? Then they can heat themselves with less wood that they gather. Not a negligible fact either.

There's also another advantage. Ecological one. The emissions of a RMH. Far better than any other stove, if working well. Except for the fly ash. It's considered particulates. Tho, far less harmful than soot, of other aromatic tars etc produced in a normal wood stove. Even with catalyst.

Plus, the catalyst, after a while, gets sooty, and doesn't work anymore.

If you're keen on numbers.

Check those two threads.

http://donkey32.proboards.com/thread/355/small-scale-development

http://donkey32.proboards.com/thread/511/adventures-horizontal-feed

Plus, there must be a reason behind MHA interest into rocket cores for masonry heaters. Don't you think?

Typically I see folks stating they cut their wood consumption from 5-7 cords with an old "smoke dragon" stove, to 3-5 cords with a modern efficient stove.  So 1/3 reduction.  Which is why my jaw drops when I see claims of 1/8 to 1/10 reductions for a RMH.  Extraordinary claims require extraordinary evidence.

Our body of evidence has been significant.   And that's just with the people that are reporting the results.

David Livingston wrote:Just a quick and I hope relevant question , these super new fires with the platinum catalyst that needs to be changed ever five years ( I have not  seen any here in France ) how much do they cost to replace the catalyst ? not the environmental cost but the actual $$$$ or how much does that add to your bills per week weather you use the fire or not or even in term of wood saved ?

David

last time I replaced the catalyst it cost me $135.  5 years lifetime is if you run 24/7 through the entire heating season.  Less frequent use will lead to less frequent replacement.

Glenn Herbert wrote:"1/4 to 1/10"

That's what I generally use in conversation too

I think I have heard from more than two dozen people that have switched from conventional to rmh - and it seems that most of the reports ....   more than half ....   are closer to 1/10th than 1/5th.   Are your numbers coming up about there?   I say 1/4 to 1/10th because there was one case I heard of that was 1/4 - and I think that guy ditched a super fancy conventional wood stove.  

Of course, nobody has to build a rocket stove. I think the aesthetics are a little wonky on some of them. There are very efficient rocket stoves out there. To each his own, I think burning with wood so long as the woodlot is growing faster then it is being cut, is always better then using a fossil fuel, regardless of device used.

But yes, I think rocket mass heaters are "appropriate tech" in the excepted meaning of the term. Are they appropriate for everyone? No, of course not. For instance, in a situation where winters are warm and a fire is only needed for cooking, they would be a bad idea, or on a 10th floor apartment, or in a workshop of a sort that is only used occasionally.

Davis Tyler wrote:
The first thing I saw when I logged in this morning is some guy who set his floor on fire: https://permies.com/t/39987/rocket-mass-heaters/Rocket-Mass-Heater-success-Saskatchewan

Chimney fires are mostly caused by people burning unseasoned "green" wood.  It's really not fair to blame the appliance

If I put my cast iron stove on the floor it wouldn't take long to set my floor on fire.  It's currently about two feet off the floor, then on the plinth, then the fire box.  

I agree with you, it's really not fair to blame the appliance.  I imagine, a lot of what goes wrong with any type of fire is user error.  

Poor construction, like poor installation, can be a hazard for anyone not following instructions.
The thing with user error in an RMH after construction is that there is so much less fire to be at risk. I have seen plenty of sparks or coals get loose when a stove door is opened for loading, while a J-tube RMH would require a spark to jump almost vertically between the sticks in the feed, but at an angle that would let it land outside the "hearth" area. In either case, floor protectors near the feed would minimize risk. A woodstove has all very hot surfaces which can be walked into by anybody careless enough to do so, while a standard RMH barrel is set back 6-12" from the nearest floor and would require a trip or reach to make contact... and that is only a hazard while the fire is burning, i.e. not for 16-22 hours a day.

Then after the barrel, the thermal mass covers any dangerously hot elements with several inches or more of dense material, and the final exhaust and chimney will have surfaces that can generally be touched or even held without danger. Compare that to a woodstove stovepipe.

Because the RMH burns nearly all combustible gases, especially creosote, there is next to nothing to condense in the exhaust, so no possibility of a chimney fire. Even if through poor design or bad operation there were some creosote deposited, it would be inside the mass where a chimney fire would be isolated from other materials.

This thread has been very informative and I've enjoyed reading the different options available when it comes to heating my home.  

I'll probably be moving in a few years and when I do, I want to drastically reduce the cost for daily use and maintenance of the home.  Where I am now, in this drafty old house, it takes $100 a month (for all electrical including lights, heat, cooking and well) plus two cords of wood to get through a hard winter.  I feel in a smaller home, I should be able to get that down to $25 a month electric (like it was in the last house) and about one cord for all heating and cooking needs over the 6 month period we call winter.  At the moment, this house has a high end, free standing wood stove and a fireplace insert.  I'm really happy with both of them, but I wonder if there isn't something that would be more appropriate for my needs and lifestyle.  

I've seen how enthusiastic people like Paul and other permies are about RMHs, and I admit, it's catching.  When it comes time to decide, I'm not going to be making my decision on enthusiasm alone.  There are a lot of questions I need to ask to determine which technology is appropriate for me.  I think this thread raises some good questions.  The cast iron woodstove has a little over 200 years of history, tinkering, trial and error, behind it, but it seems that it's only the last few decades that it's made any vast improvements.  I can see why it's still so popular.  It's nice that Rocket Mass Heaters have been around long enough now to get some strong data to back up their claims.  I'm sad I missed out on Ernie and Erica's Kickstarter and will be buying their book just as soon as I can get some cash together.  I guess my point is that we are finally getting close to a place where we can compare the two styles of home heating.

So these are the questions I get from this thread when I want to know which technology is appropriate for me?

Which uses less wood (per winter and per amount of heat)? Which uses a wood that is easy for ME to gather?  

What are the safety concerns of each style?  I know there are a lot of safety concerns regarding the cast iron stoves - they have to be so many feet away from such and such, I have to have special air inlets and several CO detectors, and the area near them has to be lined with something fireproof like stone, which is backed by fire retardant materials.  We got huge lectures from the installation people and bylaw inspectors when these were installed.  

Which will be more efficient for MY style of living? This place has a top of the line woodstove, however, to be 'efficient' there is are very specific things we need to do.  Most of the time, it isn't working at full efficiency, and to get it to moderately efficient, we need to carefully monitor what mix of hard and softwood we put in the fire box, how often, and adjust the air vent to match.  I don't know if a RMH would be less effort while it is burning, but the idea that it is providing heat when even when there is no fire, is very appealing.  

Pure efficiency, judging from the information in this thread, seems to be a matter of how we crunch the numbers.  

Which will be best for cooking?  Because I want to cook on my woodstove.  I am considering getting an iron wood fired cooker for my main cooking and RMH for my main heating.  

Aesthetics?  Some Rocket Stoves are prettier than others, that's for sure.  On the whole, I find them less ugly than most furniture and no more ugly than a woodstove.  

Matinance? I find matinaning the woodstove pretty expencive and that was built right from the get go.  Would a RMH, built out of the best materials need mataining as often?  

Which is idot proof? I have a lot of people visit the city and it's hard enough training them that fire is hot, if there is a fire in the woodstove, the wood stove is hot.  This is a very difficult concept for people born and raised in the city who have lived most of their adult life without ever encountering fire in the home.  If something as obvious as a wood stove with a fire in it difficult for them to understand, then the barrel concept in the RMH is not going to work.  I would like to learn more about this bell design.

Which will I be able to afford? I'm short on cash but long on time.   RMH is very attractive.


When the time comes, which will be the appropriate tech for me?  I don't know.  But I know a RMH is very high on my list.  Even higher after reading this thread.

Quite a discussion going on here.  I wonder, Davis, if you are trying to figure out if a RMH is appropriate for YOUR home.

So many of the factors involved are personal.  When someone has a professional job and lots of debt, (though in balance with their income) they look on time spent differently than do folks who live independently with as little debt as possible, plenty of time to DIY for just aobut everything, including rounding up materials on the cheap for years before they build something.

There is a retrofit project somewhere on line, a guy who put his RMH in the basement, had to engineer the existing concrete floor for the weight but other than that it went straight forward pretty well and he was happy with the results.

My brother, a civil engineer in New Jersey, heats his house with wood.  He does not have a RMH, some other kind of wood burner. What is worth mentioning about his place is that his wood burning set up is not in the house, it is outdoors in a shed of some kind, with insulation for that shed, and some hot air duct that must be insulated as well.  Both of those are options for anyone who wants a RMH.

I first learned of RMHs more than a dozen years ago, and have been following along ever since.  I have built several.  There is plenty of documentation that they burn wood more efficiently and without lots of high tech stuff like catalytic after burners.  Those things just don't appeal to some people.  Being in control of the things they rely on DOES appeal to some people, not all of them preppers, either.

There is plenty of evidence that RMHs are far cleaner burning than industry standard woodstoves.  They do not have to be built out of refractory materials.  Common brick can be used, as long as they were made of  the right kind of clay, fired at the right temp.  I think a person could also build it all out of cob or adobe (without straw in the mix for the burn tunnel and riser) if they knew what they were doing re materials, and the critical tolerances for getting the RMH rocketey enough.

Plenty of people use conventional state of the art wood stoves "wrong" overloading them damping them way down so that they do not have to get up in the night to reload, and the house will still be warm enough in the morning they don't freeze while pulling their long johns on before they start the fire.

If you are curious, there are DVDs (Paul Wheaton) for sale and a  complete book as well, (Erica Wisner) both from kickstart campaigns.  ( R Ranson's post above has the link for Erica's book) I have both the book and the dvd.  Hopefully some helpful person will add a link for Paul's DVD set.  Or you may be able to find it here on permies with a simple search, Or I may come back later and find them.  Right now, I need to go milk.

It's been about seven hours since we've heard from davis.  

I'm gonna call it.  



Rocket mass heaters not only qualify as "appropriate technology", but they might turn out to be the king of appropriate technology.  The best.



Further, davis tried to advocate that if money is no object then maybe the super expensive conventional wood stoves would be better.   I think we rather thoroughly shot that down.  Even if money is no object, rocket mass heaters are far superior.  

so called super efficient wood stoves are lousy compared to a rocket mass heater.  we had one of those epa rated hi class wood stoves and replaced it with rmh.  we are 70 years of age and built it ourselves according to plans two winters ago.  it works way way better than the wood stove and burns way less than half the wood.  we love it.  it is in a different universe than the expensive wood stove we had.  we think it looks great.  barrel is part of the mystique.  there is beauty in functionality.  we have posted pics on this site in the past.   michael and judy carman near lawrence kansas  btw it sure is appropriate for us.  we sold the wood stove on craigs and used the money to build our beloved rmh