Rocket Mass Heaters vs. Scandinavian / Slavic Masonry Heaters

Hello All! I am wondering if any one has done any research into comparing a rocket mass heater with a masonry mass heater in the Swiss, Norse, Finnish, Russian style. Which one is "better". Which holds heat longer, is more efficeint. Here in Siberia every one uses masonry heaters except people with large houses that have many rooms. They use high efficiency wrought iron boilers to deliver hydronic heat to the whole house. Any way, I want to put in a masonry mass heater in my house and was wondering if you thought that the rocket stove mass heater is a better option. Expereince in comparison? Scientific research?? Thanks

I can say that the masonry mass heaters produce plenty of smoke so that was what got me thinking. The rocket mass heater purportedly do not.

Justus, the "heart" of the rocket is the L or J shaped tube. There's about 3 versions, normal L for cooking usualy. The J tube, comonly used in mass heaters, and the batch L invented by Donkey Canyon and Peterberg.

The advantage of thoses 3 things, is that they barely smoke, if they smoke at all. And for sure, you could fit a rocket core into any type of massonry stove. Plus the efficiency of the burn in a rocket is amazing compared to a lot of other stoves.

Check the pics of thoses two

http://technologieforum.forumatic.com/viewtopic.php?f=19&t=27


http://batchrocket.hostoi.com/html/foto.html



Prety familiar no? They are batch rockets.

Not many pictures, but here's another one.

http://donkey32.proboards.com/thread/848/18cm-inch-double-batch-system?page=2#page=1


It is also possible to use bells like this with a J tube. Check here and at Donkey's forum http://donkey32.proboards.com/

I can't seem to find anything right now, but there's some.

And here's a site which might be of some interest to you http://www.stove.ru/index.php?lng=1&rs=16

Thanks, great info BUT...

The kuznecov stoves are nice. I've seen them before. They are beautiful, complex and huge! All things that I do not like about masonry stove (except the beautiful part)!!

Integrating a j tube with masonry stove, interesting. But the classic j tube rocket mass heater that i'm looking at seems to be ...

less complex, not so bulky as masonry stoves.

The questions is if they are better and by how much??

Thanks for the links and photos though. Masonry stoves are cool, no matter the core!!

There are three issues involved in answering your question:

1. Efficiency of the combustion system
2. Material used in the thermal mass for storing heat
3. Design of exhaust path for absorbing heat

They are all separate design options which can be combined as you wish.

#1 - A J-tube is a very efficient combustion system for wood. It accomplishes this by providing 2 chambers for burning. The first chamber or burn tunnel ignites the wood and releases the volatiles. The second chamber (heat riser) provides an insulated space for the continued combustion of the volatiles. If the fire is allowed to cool down (by removing heat too soon), the volatiles are not combusted and they go up as smoke. There may be another way to burn wood more efficiently, but so far the insulated 2 chamber system is it. If any particular masonry heater has a lot of smoke going out of the chimney, it is not extracting the most BTUs from the wood and is probably less than 50% efficient.

#2 - The rocket mass heater described in "the book" and on the Permies blog uses regular clay/sand for heat storage. Traditional European/Russian masonry stoves use dense, conductive fireclay brick or slabs. The latter actually has better characteristics for thermal mass, but it is more expensive than regular clay.

#3 - Both rocket mass heaters and traditional masonry heaters use flues (contraflow as a subtype of flue) for the exhaust path for absorbing heat. Kuznetsov developed the idea of large chambers or "bells" as the exhaust path. Bells have been shown to absorb more heat from the exhaust than flues because they allow the gases to stratify within the chamber leaving the hotter gasses in place longer. Also, the ballast gasses in the exhaust (primarily Nitrogen) has never gotten as hot and will fall out of the exhaust path sooner in a bell system. I would think a bell system would be less complex, internally, than the same size of masonry heater using a contraflow design.

Bells don't have to be huge. But, if I lived in Siberia, I would want several large bells.

We have implemented a 4" j-tube with a 6' tall, 18"x18" bell made from clay chimney flue liners. It keeps a 700 sq. ft space warm in Texas.

If you check the blog in my signature, we have an article comparing materials used for thermal mass and another article on bells vs. flues.

Hey Cindy! Thanks for replying! Interesting about the bells. Just all of the cold climate kuzsnetsov stoves i've seen are HUGE! That's where the idea came from. And, no offense, but you don't need much to heat a house in Texas!!

But I was wondering, have their been tests done on efficiency of J tube combustion as opposed to standard fire box combustion? I remember reading a paper where some university test several masonry mass heaters (slavic style, firebox with serpentine flu's in a masonry wall) and found, no unsurprisingly for me, that they were far from the advertised 90% efficient but closer to 65%-68% total thermal efficiency.

So the Q is this. How can a rocket stove do 10 times better than a standard stove without being over unity? especially when comparing with the modern "King Blaze" style stove which basically try to do the same thing as the rocket stove and return the gasses?

Have any real scientific tests been done.

I always get real suspicious win I see claims like "Heat your home with 1/10th the wood!" IT seems incredible to me. I go through about 14-15 cord a winter. Btu loss is Btu loss any way you bend it and that loss needs to be replaced with heat. Am I missing something??

I would give my left leg if I could cut my wood consumption in half, let alone by ten times. I think end times is crazy. But in half, I could get really excited about that!

kuzsnetsov stoves i've seen are HUGE

I thought all the masonry heaters in Russia were huge. Are you saying that the Kuzsnetsov stoves are larger than the flue or contraflow heaters?

have their been tests done on efficiency of J tube combustion as opposed to standard fire box combustion?

Not by any official organization. It has to be fed in such a different manner than the wood-burning devices for which the tests are currently designed, that the protocols are not applicable. In order to get the J-tube combustion system tested, someone someday will first have to pay to have some standards designed by a company which does that sort of thing. Once the testing procedure and standards are established, then a j-tube system could be tested against some other specific wood-burning device.

I basically agree that a claim of 10x is probably overreaching since no one knows what the target reader is using now. On the other hand, the open fireplace which is traditional in U.S. homes is so inefficient that it actually has a negative effect on the total heat in most houses. So, maybe you could get a 10x improvement there.

The other clear fact is that many people have built rocket stoves and are using considerably less wood than they did with a standard cast iron wood burning stove. Such a stove is the usual wood-burning alternative U.S. people think of when one says wood heat. There are 2 parts to the improvement: 1. the combustion efficiency of the j-tube and 2. more of the heat is being retained in the house (by storing it in the cob bench).

Do you have visible smoke going up your chimney most of the time when you are burning wood now?

If so, your heater is not burning up the volatiles where 40-60% of the BTUs in the wood are found. You could conceivably cut your wood use in half by replacing the combustion system with something which keeps the entire combustion area hot and consumes the volatiles. The J-tube as described in Rocket Mass Heaters is one design which does that. And no one will ask for your left leg in return.

university test several masonry mass heaters

Were any of the tested units based on bells instead of flues?

http://donkey32.proboards.com/thread/1072


http://donkey32.proboards.com/thread/355?page=2

It seems to me that the standard russian contra flow stove is quite a bit smaller than a bell stove, or Kuznetsov Stove.

Thew were not testing bell stoves, just flu based contra flow.

Satamax Antone, thanks great links!

Justus Walker wrote:Hey Cindy! Thanks for replying! Interesting about the bells. Just all of the cold climate kuzsnetsov stoves i've seen are HUGE! That's where the idea came from. And, no offense, but you don't need much to heat a house in Texas!!

But I was wondering, have their been tests done on efficiency of J tube combustion as opposed to standard fire box combustion? I remember reading a paper where some university test several masonry mass heaters (slavic style, firebox with serpentine flu's in a masonry wall) and found, no unsurprisingly for me, that they were far from the advertised 90% efficient but closer to 65%-68% total thermal efficiency.

So the Q is this. How can a rocket stove do 10 times better than a standard stove without being over unity? especially when comparing with the modern "King Blaze" style stove which basically try to do the same thing as the rocket stove and return the gasses?

Have any real scientific tests been done.

I always get real suspicious win I see claims like "Heat your home with 1/10th the wood!" IT seems incredible to me. I go through about 14-15 cord a winter. Btu loss is Btu loss any way you bend it and that loss needs to be replaced with heat. Am I missing something??

I would give my left leg if I could cut my wood consumption in half, let alone by ten times. I think end times is crazy. But in half, I could get really excited about that!

How do you get 10:1 improvements?
Simple: We have a lot of people heating with relatively crude technique in woodstoves, which themselves are pretty much crap for heating. They are sold as 'space heaters', not for heating an entire home; yet most people in the USA who heat with wood try to do it with a metal, box-like woodstove.

Even when these light-weight stoves test relatively efficient under ideal conditions, the test is rigged in their favor (graded on a curve where 85% counts as 100%). Most efficiency tests are also performed at the manufacturer, not at the independent lab (the EPA labs just assign a rating based on the general type of stove). Under test conditions, you have dry wood, and operators with enough experience to know that burning it clean produces more energy than a smoldering, smoky fire.

Next, these stoves go out into the real world, where they are rarely operated under ideal conditions. The biggest difference occurs at night, when most people heating with a thin-walled woodstove try to 'bank' a fire to keep embers alive in the stove all night. This banked fire produces a lot of smoke, and wastes that 50% of the fuel value that Cindy was talking about. Most stoves smoke a little even when running relatively hot; they may be extracting 70% to 90% of the fuel value at full burn (at a guess). But when they are banked down, they run a LOT less efficient on fuel. That's where mass storage comes in: it essentially eliminates one or two of those long-burn cycles from your day, so that saves maybe 60% of your fuel right there.

If you also are in the habit of burning wet wood, you lose something like 50% (can be more) of your fuel value to drying the wood while already in the fire, and to steam extinguishing the secondary flames.
(I see far more woodpiles out under trees, or undersized woodsheds with a big exposed woodpile 'out back', and I've only seen a few really good, capacious wood-drying sheds among our many site visits.)
If you switch to a heater that uses 1/2 to 1/3 the wood per year, your tiny woodshed is suddenly adequate to your actual needs, which means you are now burning drier wood. Especially the first two years, if you are enjoying two-year-seasoned wood left over from the switch. This might easily take you down to 1/4 or less, if wet wood was part of your problem before.

The 1/10 the wood was based on anecdotally reported experience, several people who said they swapped out an older woodstove for a rocket mass heater in the same space (otherwise unchanged), and the wood use dropped from 4-5 cords per winter to something like 1/2 cord.

We typically see a drop to about 1/4 the wood for most people going from a more recent woodstove or insert to the rocket mass heater. Or using the rocket heater for primary heat but continuing to use a parlor or kitchen stove (they don't separate the wood sources for each stove). Sometimes they estimate by wood delivered; sometimes they estimate by number of armloads per day. It's pretty loose.

We sometimes see smaller drops if the person had previously optimized their wood heat quite a lot, and a rocket was their last and only change. In one case, the owner reported using about half the wood, but was splitting that wood between her new rocket and a previous wood-burning kitchen stove.
When you consider wet wood, how much of the heating season they spent at home, whether their home is actually insulated, whether they lowered the indoor temperature because they were sitting on the warm mass, or whether they have shoved the heater in a basement or annex and expect the same results as someone who enjoys direct heat in the living room..... The noise can get bigger than the data.

I would not expect these comparisons to hold for going from one masonry heater to another.
Masonry heaters already have the mass-storage advantage, and thus can be run more efficiently than most thin-walled woodstoves in the USA.
Masonry heaters are so heavy (and expensive to install), that nobody wants to switch from one to another!
So it will have to be a deliberate lab test, or else maybe two identical wings in a large house belonging to a rich private experimenter.
I do not know if anyone has done this test yet. My best bet would be to ask some of the folks who work with both types of designs. There are some North American MHA guys who are curious, like Erik Moshier in the Midwest, Jason Temple out here in the Pacific NW, or John of Red Clay Construction in PEI. Or Flemming Abrahamsson at fornyetenergi.dk. They might have a better 'gut' idea of which type of heater gives the most bang for the buck, even if they haven't done direct comparison tests. But bear in mind that most of them have done a lot more masonry heaters and maybe one or two rocket heaters, since rocket heaters are not as easy to permit here.

Another thing you can do, just to satisfy your own curiosity, is to run your heat-loss BTU calculations for your current house. Then find the theoretical fuel value of the wood (not the value adjusted for heat loss to smoke). That should give you some idea how much the minimum wood you could burn, compared to the amount you now use.

I have done this twice with different heat-loss calculators for our current home. We also weighed every stick of wood we burned for two months straight, in addition to doing the usual rough estimates by volume for the entire season.

In the first case, the calculation result was that we were extracting 95% to 100% of the fuel's theoretical value. I think I probably did not allow for the days we were not home, so our house was colder (heat load is less if you keep the room cooler), and we used the wood "saved" during these absences to produce the actual comfort heat at other times.

In another case, the calculation result was that we should theoretically need about twice the wood that Ernie believes we are actually using. I think we may have burned a little more, but still less than the calculations predict. I can't entirely account for that one! except to consider that again we were gone from home a week or two here and there in the fall and winter, and we do prefer to wear a sweater rather than go out to the woodshed twice in one day. But I also think we may need to do a more careful before-and-after count of the actual wood use, and the actual temperatures at our actual location.

These numbers appear to have greater margins of error than the result we are trying to find. I would not trust them for your purposes. But I do find them encouraging.

I would be delighted to be involved in BTU-related tests to see how much heat a rocket heater really does extract and store, if anyone cares to think up a protocol that can be done with available equipment (or to help fund the equipment / independent tests). I don't know of any lab that is currently set up to do these tests at any reasonable fee, as they'd need the heater to be enclosed in a 'standard' space and track the heat output over many days to "see" the storage effect. But then, my income compares to many educated professionals in roughly the same way that my heater's fuel needs compare with the 'norm'. I might need to do a crowdfunding campaign, to build the budget to do some of these tests or get the equipment for continuous monitoring in a random facility like our house.

I feel like I've written up these rough numbers, and excuses, far too many times.
I'm going to post a straw poll regarding the crowdfunding idea.

Yours,
Erica W

I just wanted to chime in with some additional questions on this front.

In the next year or two I am looking at building a mass heater for my house near Hillsborough NC. For many years I have been contemplating building a masonry heater, but I've also done a lot of research on the RMH (including Ernie and Erica's DVD set -- which was great!). I am now leaning towards the RMH, but I want to ask why someone would have a masonry heater over a RMH?

Here are Pros and Cons that I can think of for both: (please correct anything that is considered inaccurate)

Both are going to be good at burning efficiently and storing heat in mass. Both are beautiful in their own ways, but I would guess that a masonry heater would be more commonly accepted as beautiful without a lot of explanation

Rocket Mass Heater
PRO: relative cheap, technically easier to build, can use a lot of local materials, easier to repair, easy to have a heated bench/day bed
CON: shorter life span (15 -25 years before rebuilding the burn tunnel or replacing the barrel), needs to be burned more often (is this accurate?), cob is a less efficient material for heating quickly, large hot metal cylinder that babies can burn hands on (same as a metal wood stove), more difficult for re-sale (anyone have experience otherwise?)

Masonry Stove
PRO: can be burned 1 - 2 x a day to maintain even temperature, can radiate heat more quickly (especially if made with stone), fairly low surface temperature (not likely to burn hands), very long life span if built well, more likely to be commonly appreciated as attractive and likely an easier point for home re-sale, has potential for easily adding a baking oven door
CON: EXPENSIVE (even for a skilled DIY person, you'll likely spend $3K-$4K to build one of these things; MUCH, MUCH more if someone else builds it for you), technically difficult to build correctly, difficult to repair if/when needed

Did I miss anything and/or get anything wrong? I am willing to put the money and effort into building a masonry heater if it is really that much better than a RMH. However, I am having doubts that it is so much better to warrant the cost. I could use a little discussion to get my mind solidly around one of these two options.

There are (at least) two areas to be studied with respect to the difference between a rocket mass heater and the masonry heater.

1. The combustion system. Here the J-tube design is known to be excellent at extracting BTUs from the wood burned. Generally, the firebox in masonry heaters is not as efficient. They can claim a high rate of efficiency because masonry heaters are storing nearly all the heat being produced.

2. The system for immediate release (a steel drum in the rocket heater) vs. heat storage.

Ianto Evans' style of rocket mass heater releases a lot of heat into the room immediately via the steel drum which gets really hot. Our tests based on taking temperatures at various points show that up to 50% of the heat goes out through the steel drum. Consequently, some people cover their steel drum with cob. The traditional wisdom on this is that the steel drum cooling the exhaust helps move the exhaust out through the flue. In our designs, we have eliminated the steel drum and used bells (lined with dense firebrick) instead; we have no trouble with chimney draft or back puffing into the feed tube.

A masonry heater doesn't have any steel, so it is slow to heat up. Instead of cob, they are made with dense refractory material which is better (than cob) at conducting and storing heat. A masonry heater only needs to be fired intermittently because of the quantity of refractory material storing the heat. There are kits for building masonry heaters, but they are expensive, as you noted. The one I saw had great slabs of dense refractory which were stacked just so to make the flue of the system.

Both systems yield a pleasant sort of heat which is nicer to live with than forced air.

Nathaniel Rogers wrote:
Masonry Stove
CON: EXPENSIVE (even for a skilled DIY person, you'll likely spend $3K-$4K to build one of these things; MUCH, MUCH more if someone else builds it for you), technically difficult to build correctly, difficult to repair if/when needed

It sounds like you've done at least some of your homework here, so I'm curious what's your basis for this $3k-$4k range?

I'm planning on building a single-bell masonry heater this summer, and here's my rough budget:

Two sacks of castable refractory to build Peter Van Den Berg's firebox: $150
Front door and cleanout door: $200
Chimney pipe (single wall, not the expensive stuff- don't have to go near any flammables, thank goodness): $50
Rock wool insulation for top and back: $50
Surprises and problems: $100
Homemade adobes/CEBs for the walls, $0
Mud mortar, $0

That only makes $550. For $3k-$4k in materials, you must be planning on buying brick or stone? Firebrick flues rather than plainer masonry bells?

Hi Cindy,

I took a look at your dragonheaters.com website. Those are interesting designs and systems. One thing that I do like about the RMH is that the metal drum does give you that immediate heat response, but I also like the idea of a system that can be burned less often and can store a larger percentage of the heat in a mass buffering system.

Hi Mike,

The $3K - $4K estimate comes from two sources. The first being a design manual for a Finnish masonry heater from MaineWoodHeat.com (https://mainewoodheat.com/shop-maine-wood-heat/publications-manuals/the-finnish-fireplace-construction-manual-%C2%A91984-with-a-2006-update/
). Its part list comes to $3K 20 years ago and I can only imagine that it is at least $4K now. The second was from a blog about a guy who built a masonry heater and the materials cost him $3K. Both are flue type masonry heaters.

I read "Masonry Heaters" by Ken Matesz a few years back. I can't remember if his designs were more flue or bell based. At the time I liked the idea of designing my own heater, but I've since grown towards the idea of building a tested design which is why I got the Finnish Fireplace manual.

Did you design this heater yourself or are you working from an existing design? Do you have links for the masonry heater Peter Van Den Berg's firebox? I googled him and found links for a number of stoves, especially rocket stoves. I need to look back at the Matesz book, but do you have any preferred resources for bell masonry heater designs? Also, what size space is your heater going to be heating? I am looking to heat about 1500 sq ft.

If you are using homemade adobes for the outside walls/thermal mass, is there much benefit of this system to a RMH as they will have a similar thermal delay in the mass storage due to the cob/adobe's fairly low thermal responsiveness? If I build a masonry heater I would lean towards refractory materials for the core and brick for the exterior and mass. Brick isn't as responsive as stone and especially soapstone, but it is a fair bit more responsive than adobe/cob (if I am remembering right). Do you feel that homemade adobe bricks will hold up to the thermal stresses of a masonry heater? Also what is a CEB?

Mike,

Just one more question (for now), where are you sourcing your hardware (doors)? Thanks.

Thanks, Nathaniel, good to know!

Working backwards:
Hardware: I haven't researched quality, etc, and depending how my year goes, i may try to build the doors myself. But if not, there seem to be a handful of readily accessible vendors.
Here's an 8" square cleanout door, $44 LINK
And an 8" x12" suitable for a firebox door: LINK

Adobe:
Durability, yes. From what I understand, being able to use mortar of the same material as the blocks means the entire assembly has the same coefficient of expansion, and this helps prevent cracking. The bell doesn't see the same high temperatures as the firebox, so it doesn't have to resist spalling, etc.
(CEB stands for Compressed Earth Block- it's an adobe block you make by compaction, rather than by wetting and pouring into a mood.)
Responsiveness: you're right. Quantitatively, earth is an inferior masonry choice vs. brick or stone. Inferior, though, doesn't mean bad. It just means less great. So for me, when I account for the better cracking resistance, the $0 price, and the fact that i like the look, it's the right choice. I don't mean to imply it's optimum for everybody.

Design and layout: This will be the only heat for a rather challenging house. It's old and drafty (I'm working on airtightness, but there's a long way to go) and the heater is on an outside wall at one end of the house. Ideally, you have it at the middle so the heat can reach everywhere. We have a tough time keeping the far end of the house warm with the woodstove, so the masonry heater will be no different. On the positive side, the house is small, a hair under 1000 sf.

I'm designing the stove myself. It will be pretty simple- a rectangular space with a center column to hold up the ceiling. The essence of a bell, of course, is that exhaust exits at the bottom. That's about it. I know there are gains to be had by designing a double bell, but I don't fell quite up to the challenge.
The main resource for bells is www.stove.ru, the website of Igor Kusnetsov. He's even got a series of brick-by-brick drawings, under the link on the left of the page "working drawings". Matesz doesn't really address bells at all.

Van Den Berg's firebox is the outcome of a couple of years of really fascinating experimentation. The Sketchup files are here:
(There are three versions: a castable one, and two versions made from different sized firebrick.)
http://donkey32.proboards.com/thread/691/project-horizontal-feed-batchbox-model


Hope that helps! I'm a little uncomfortable holding myself out as knowledgeable here- I feel like I should include the disclaimer that I've just done my reading. I haven't built it yet. When I do, you can bet that I'lll have the pictures here Permies.

Mike, keep us informed on progress. im not that far, and could toss in a few hands on your build if needed if the timing is rite.

Hi Mike,

Thanks for the info. Are you making the CEB's yourself with a hydraulic press or something, or are you able to rent one of those fancy CEB machines that you can see in youtube videos? The CEB seems pretty damn cool; basically rammed earth blocks with potential for adding cement or other component for stabilization.

I wasn't meaning to say that adobe/cob wouldn't work well as a heat storage mass, just that they aren't as optimal as other options. Do you know how CEBs compare to brick? I would have to imagine that they would be very similar to brick given their density. Definitely an interesting option. If I won the lottery, I'd have a gorgeous Tulikivi soapstone masonry heater installed in my house, but that isn't tooo likely.

Leaning back towards my original question -- did you ever consider a RMH over a masonry heater and if so, what lead you to go with the masonry heater?

Hi Mike,

No need to reply about how you are making the CEBs. I found your thread about the homemade CEB press. Pretty cool.

Just to clarify... Peter van den Berg designed several enhancements to Ianto Evans' original firebrick design for the combustion system. A discussion of these is found on page 111 of the 3rd edition of Rocket Mass Heaters. Dragon Heaters licensed his design for commercial production in the U.S.

Nathaniel Rogers wrote:Hi Mike,
Leaning back towards my original question -- did you ever consider a RMH over a masonry heater and if so, what lead you to go with the masonry heater?

I didn't. I mean, I considered it, but it didn't take long, because I hate the look of the barrel. It's purely taste, but for me, the barrel in the room in a non-starter.

That's the main reason. Second would be my heating needs- Michigan gets cold and stays cold, without a whole lot of day/night temperature swings. It's just cold. So responsiveness is a low priority for me. I don't need it warm suddenly, I need it warm for four straight months! I don't need responsiveness, but I would like some ease of tending. This year, we've got an infant to wake us up at night so we can feed the woodstove. In the future, I'd like to sleep through the night with a woodburning arrangement that I only feed twice a day.

So those were the two reasons for me to settle on a masonry heater, rather than a RMH: aesthetics and batch burning.



Now. That said, what I'm doing I think would technically be a hybrid of masonry stove and RMH.
Like Satamax said toward the beginning of this thread:

Justus, the "heart" of the rocket is the L or J shaped tube. There's about 3 versions, normal L for cooking usualy. The J tube, comonly used in mass heaters, and the batch L invented by Donkey Canyon and Peterberg.
The advantage of thoses 3 things, is that they barely smoke, if they smoke at all. And for sure, you could fit a rocket core into any type of massonry stove. Plus the efficiency of the burn in a rocket is amazing compared to a lot of other stoves.

And that's what I'm doing, putting the "batch L invented by Donkey Canyon and Peterberg" "into any type of massonry stove."

As Cindy noted above:

Generally, the firebox in masonry heaters is not as efficient.

So this is a way to overcome that. Use the highly-efficient, burn-twice-a-day firebox in the easy-to-build, steady/unresponsive heat extractor. The Peterberg batch box in a CEB bell.

Mike, another idea i quite like.

http://heatkit.com/research/2009/lopez-rocket.htm


By the way, you don't necessarily need a barrel.

I have gotten this, a stainless steel column, from the wineyard of an acointance. Closed at one end.

http://donkey32.proboards.com/attachment/download/828

You could also hide the barrel. I have often advocated the use of a dry stacked brick latice around the barrel. It cuts the uglyness of the barrel, and adds a bit of mass.

Satamax Antone wrote:

http://heatkit.com/research/2009/lopez-rocket.htm

Wow, what information! That's a goldmine!

Thanks, Max- I hadn't seen that yet.

Satamax Antone wrote:
http://donkey32.proboards.com/attachment/download/828

This link has an error that says "guests are not allow to download."
Could you post or paraphrase the contents?

Hi Mike,

Thanks for all of the input and information. I'll have to spend some time doing research into bell designs and factoring that into my decision. I am similarly more inclined towards a masonry heater for the aesthetics and decreased need for frequent burns. The cost was putting me off, but your info has changed that factor. Down in NC I do have less of an issue with more frequent burns as I wouldn't be running the heater as many days, or for as many hours a day as you would in Michigan. I also have to look into what my local building office will allow me to get a permit for. I look forward to your future posts about your project on Permies.

Satamax,

That Lopez Labs page is awesome. That is some fantastic data on various configurations.

Cj Verde wrote:

Satamax Antone wrote:
http://donkey32.proboards.com/attachment/download/828

This link has an error that says "guests are not allow to download."
Could you post or paraphrase the contents?

CJ, it's the pictures in that thread, i tried to post to ilustrate the different barrel.

http://donkey32.proboards.com/thread/1017/pure-genius

Hey everyone. This is my first post on this site after Google keeps directing ALL my questions to you and finally signing up.

Although this thread is more than a year old, I thought I would share current personal experience as to why a 10:1 efficiency would be somewhat in the realm of reality. I have attached 2 pics. One of the fireplace and the second of the "super efficient" wood stove my family have been using for the past 5 or 6 years.

This is supposed to be a decorative stove that my grandfather had installed years ago, with my uncles blessing. Well, now that I have moved in to help my grandmother after my grandfather has left us and my uncle no longer lives here, this is the LAST season this wood stove will be in the house. Come hell or high water it WILL be replaced with a much more efficient and LEGAL wood stove. Unfortunately my grandmother is too old school to convince her of anything else radically different. This thing has scared me for as long as it's been here. But back to the reason I posted this.

We have forced gas heat in the house, about 1400 square feet and the ducting wasn't well maintained. The thermostat in the house is kept at a minimum of 66 to 68 degrees F so at night the house doesn't get freezing if we don't have a fire in the wood stove. Now, that wood stove will heat the whole house really well with a good box fan blowing around it, but it will DEVOUR the wood and we have to keep feeding it every hour or so. So even with a gas furnace keeping the house at a somewhat comfortable ~67 degrees, we can go through 3 to 4 cords of wood a season. And when we fire it up we smoke out a lot of the neighbors. I hate the damned thing because as an engineer I can see the inefficiency pouring out of the chimney. As well as my uncle "teaching" my grandmother that keeping a smoldering 'indian fire' and sitting next to it is the best way to keep warm. Drives me absolutely insane.

So in conclusion, if people, which are quite a few around here, use this type of wood stove to get supplemental heat, imagine if we had an actual thermal mass wall with a 1 or 2 time a day burn. We would probably only go through 1 cord a season, and save hundreds in gas bills.

EDIT: Oh, and we live just outside of Portland, Oregon in the Pacific Northwest, near Mt. hood at an upper elevation, for geographical reference.

Here ya go buddy. its not the best photo work since I only used MS Paint. but heres the idea to please everyone. Grandmother gets to keep the wood stove and you all get to enjoy awesome efficiency and radiant heat from a batch box conversion.

1 pull the wood stove and flip it on its side.
2 make a custom refractory sleeve to fit inside the flu exit to save the metal.
3 line the stove with thin fire brick
4 build the exhaust and manifold that everything will plug into from the horizontal on up into the chimney
5 build heat riser out of fire brick and plug batch box (former wood stove) heat riser into manifold
6 lay brick around all the horizontal exhaust and use your favorite mass material to fill it all in.
7 finish brick and place half 50 gal barrel on top to complete it

Why flip the woodstove on its side? Its internal proportions are reasonably close to proper batch box dimensions as is. Line the stove with firebrick to get the firebox and port dimensions given in the table:
http://donkey32.proboards.com/thread/734/peterberg-batch-box-dimensions

The heat riser would come up about where the existing stovepipe connection is. This wouldn't fit well inside the fireplace, so you would need to spin it left or right, whichever puts the door in the most convenient position for feeding given your room layout. This would put the riser at the right or left side of the hearth, and you could build a bell on the hearth enclosing all but the woodstove door. Maybe you would want to leave more of it exposed to make it seem more like the woodstove is still there. Brick in a channel from the bottom of the new bell space up to the chimney throat.

Glenn is correct i am sure it could be done as creative as buddy sees fit i guess as long as it suits him. i was only trying to keep it facing front. Glenn has good ideas. a batch box regardless which way it faces would make grandma happy she gets to keep the stove.

There has been recent research on the peterberg batch box showing that it is possible to shorten the riser by up to half and still get a good burn. Details are in threads on Donkey's forum, which I haven't kept up with lately. Given this, it *might* be possible to remove the legs from the woodstove and have enough space to have the riser inside the fireplace cavity, with the bell coming out to envelop the stove on the hearth and reaching up as high as desired. You would need to have enough space inside the fireplace to build an exhaust channel going from the floor to the chimney throat. Exact dimensions of the existing layout would be critical to planning this.

This isn't the same research info, but it has similar results. Also links to sexy videos of flames
http://donkey32.proboards.com/thread/1690/walker-core-variation

Nathaniel Rogers wrote:Hi Mike,

Thanks for all of the input and information. I'll have to spend some time doing research into bell designs and factoring that into my decision. I am similarly more inclined towards a masonry heater for the aesthetics and decreased need for frequent burns. The cost was putting me off, but your info has changed that factor. Down in NC I do have less of an issue with more frequent burns as I wouldn't be running the heater as many days, or for as many hours a day as you would in Michigan. I also have to look into what my local building office will allow me to get a permit for. I look forward to your future posts about your project on Permies.

Satamax,

That Lopez Labs page is awesome. That is some fantastic data on various configurations.

Hello Satamax,

If you are going to invest 2-7+ days of your time, money and energy building a reliable, safe heating system for your home and family you are better off building a masonry heater. They have been in use for around 1,000 yrs and they work 99.9% of the time without any issues as long as they are built according to a set of plans that has been trial tested by experienced masonry heater builders and not just weekend pyro's. Any masonry heater that is properly built will out live the builder and most likely the next 5 generations. Yes, they might take a day or 2 longer to build than your typical rocket stove and cost you $500-$1,000+ dollars in materials but you are building something that will last potentially 100's of years. There is considerable testing that has been done and is still being done on masonry heaters in North America and in Europe and they have proven to be safe and work 99-100% of the time and not be temperamental like a rocket stove can be at times. Masonry Heaters are also listed in the International Residential Building Code so they can legally be built anywhere that they allow wood burning. Since they are listed in the IRBC and if built according to ASTM 1602 then the majority of all insurance companies will also cover them being built in your home. Yes there are kits and systems for building masonry heaters that will cost from ~ $1,000-$7,000 but all of these systems are guaranteed to work if built properly. As far as testing and efficiency of a masonry heater goes compared to a RMH just go onto the Lopez Labs page to see some of the work that Norbert and the rest of us have done testing masonry heaters. The Europeans have 1,000s of tests done especially on Kachelofens.
Rocket Mass Heaters are still deemed experimental.

Not all masonry heaters are that difficult to build, yes the require some gluing together of firebricks but so do RMH's. There are simple Russian Bell Heater plans that will outperform any RMH in performance and longevity, yes they might take a day or 2 longer to build and cost you a few hundred dollars more but in the long run they will outlast and out perform and you wont have to tear it apart and rebuild it in the next 100 yrs.

Don't just build something because it is cheap and fast. You are only given so much time on this earth that you will never get back. Choose wisely.
Eric Moshier

Eric, thanks a lot for your reply.

About the "fact" that masonry heaters are more efficient than rocket mass heaters, i will have to disagree.

As people say; it all depends.

On the type of rocket core.

On the heat harvesting solution.

On the chimney behind.

It's sure that a cobbled up J tube, with a bench with tubes can seem very inefficient. Tho, some testing done by Peter Van Den Berg, has proven the J tube to be a very capable contender on the efficiency side. Still a fair bit of excess air. But the numbers are real good.

http://donkey32.proboards.com/thread/355/small-scale-development?page=6#page=2



And if you can beat the CO readings of a J tube, with a masonry heater, you are very skilled.

The bench and horizontal tubes, i'm not too keen on. I will agree with you, on the fact that there is better heat exchangers and accumulators. But it soo cheap that it makes it worthwile.


I will add that there's no money to gain here. Most of the rocket builders are here to save money, no to spend any.


When you say, 1000 dols to make a masonry heater. Let me doubt it. It's your job obviously. But If i have read some of the MHA papers correctly, for a long flywheel mass heater. You often hear about 5 or 6 tons of firebricks. Let say, 1700 bricks, that's already a fair chunk of money to shed upfront. I have seen some of your pebble stoves. That would make it cheaper. But there is the concrete problem comming into play in this case. Which is not realy that green a material. And costs a bit too, compared to cheap as dirt cob.


And, then, when you delve into Batch rockets, and bells. I realy doubt any conventional mass heater would compete with the evenness of the burn, and it's efficiency.

I agree, for the most part, batch rocket mass heaters are just a smidge different. The core or engine not being a simple firebox, with added air channels.

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


I would like to convince you.

Satamax Antone wrote:Eric, thanks a lot for your reply.

About the "fact" that masonry heaters are more efficient than rocket mass heaters, i will have to disagree.

Don't get me wrong, I love what is being done with RMH, but when some of the people on these forums talk about figures & numbers that can't possibly add, that is when I get a little disgruntled.
The bullshit stops when you have real test data.

You can disagree, just look at the hard data and compare a masonry heater to any J tube style heater. Plus a large J-tube firebox is only 8"x8" so you cant get much wood into that space and you are only going to get up to ~7,000Btu's out of any given pound of wood and that is with a heater with around 80% overall efficiency. A typical well insulated home will require around 25Btu's per hr/ sq.ft. so a 1,000s.f. home will require ~25,000 Btu's/hr in Northern MN in January. That is 3.6#/hr or around 86#/24hr heating cycle. A J-tube with an 8x8" firebox will only hold about 12# of wood/fire so you would need to fire the RMH 7X to get the required amount of heat for a very small home.
This is what always seems to mystify the people who say you only burn 10% of the wood. Not Possible. There are only so many Btu's in a pound of wood and you can't magically get more our of it.

As people say; it all depends.

On the type of rocket core.

On the heat harvesting solution.

As far as heat harvesting goes, it all goes to the material that you use and yes dirt and soil is cheap but the density is severely lacking compared to brick and stone. The density is what stores the heat.

On the chimney behind.

It's sure that a cobbled up J tube, with a bench with tubes can seem very inefficient. Tho, some testing done by Peter Van Den Berg, has proven the J tube to be a very capable contender on the efficiency side. Still a fair bit of excess air. But the numbers are real good.
Peter is doing some wonderful work with his batch burner, but he is basically turning the rocket stove into a masonry heater. The excess air is what kills your efficiency numbers.

http://donkey32.proboards.com/thread/355/small-scale-development?page=6#page=2


And if you can beat the CO readings of a J tube, with a masonry heater, you are very skilled.

Unless you are building your fireboxes with 100% underfire air like we did 30+ yrs ago the majority of all masonry heaters built with the Eco-Firebox have CO numbers of ~ .04-.08. This firebox is now the only firebox that can be built in Germany, Austria, France..
http://www.heatkit.com/research/lopez-2014-03-01.html

The bench and horizontal tubes, i'm not too keen on. I will agree with you, on the fact that there is better heat exchangers and accumulators. But it soo cheap that it makes it worthwile.
The bench is fine if you have a lot of floor space, like 4'x8' with a typical RMH. A standard masonry heater has a footprint of ~2.5' x 4' w x 7' h.


I will add that there's no money to gain here. Most of the rocket builders are here to save money, no to spend any.

I wasn't trying to sell anything here, just dis spell some of the myths that were being thrown around about masonry heaters. I think it is great that with around 90 firebrick and a 55gal. drum that you can make a RMH, add on 3'x6' of heated bed with metal chimney pipe and lots of clay,rock,& sand and you have a decent heating system.
You can also build a simple double bell heater, or even a contralflow heater with around 300 firebrick (~$500) and 200# of refractory mortar ($150) or just clay mortar (which is not technically legal). You can finish the outside of the heater with the same cob/adobe that you build a RMH with or buy ~90-4" solid concrete block ($140 with mortar), or local stone, or reclaimed brick... for free. Use and old fireplace door or buy a new one for $200+. Yes a little bit more educating is involved with laying stone or brick but when you are finished you will have a heater that will work 99.9% of the time and it will have a firebox large enough to shoot out around 360,000Btu's on 1 fire and last 100+ yrs before needing the firebox rebuilt. Plus is sits in a 3'x4' space in your house not a 4'x8'.
Another bonus is that a masonry heater is listed in the IRC so you can legally build them and your insurance company will cover them.
A smaller masonry heater for heating ~1,000s.f. normally only needs 200 firebrick.

When you say, 1000 dols to make a masonry heater. Let me doubt it. It's your job obviously. But If i have read some of the MHA papers correctly, for a long flywheel mass heater. You often hear about 5 or 6 tons of firebricks. Let say, 1700 bricks, that's already a fair chunk of money to shed upfront. I have seen some of your pebble stoves. That would make it cheaper. But there is the concrete problem comming into play in this case. Which is not realy that green a material. And costs a bit too, compared to cheap as dirt cob.

The facts are above and I have built over 300 heaters. I built one monster triple bell heater that was 16' tall but there were only ~1,500 firebricks, I have never seen one to take 1,700 and I have seen a lot of heater building plans. A normal heater will take ~ 300 firebrick.
There might be some monster Russian heaters that are 3'x8'x7'h but almost no one builds those old inefficient styles anymore.

And, then, when you delve into Batch rockets, and bells. I realy doubt any conventional mass heater would compete with the evenness of the burn, and it's efficiency.
Look at the data. J-tubes don't come close,too much excess air. Peters batch box is very good, but to me it is more of a masonry heater hybrid than a RMH. Horizontal firebox, fed into a vertical channel which goes into a Bell or more channels. Yup, sounds kinda like a masonry heater.

You keep thinking that Peters batch firebox with a Bell is not a masonry heater. Why, just because he uses an insulated firetube (that is very expensive) and then Bells/chambers (Just like a Bell Heater). He is getting close to the same numbers that we have been getting for years. Plus it looks an awful lot like a masonry heater.
Normally if it walks like a duck & quacks like a duck..

I agree, for the most part, batch rocket mass heaters are just a smidge different. The core or engine not being a simple firebox, with added air channels.
Peters batch box with added air channels is basically turning into a masonry heater, just Peters version of one. Peter is doing some great work, I like him very much.

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

I would like to convince you.

I know the design, testing and data behind all 3 units here (J-tube, batch box, & masonry heater). Once the data hits the table all the BS stops. It's hard to argue with hard data.

Great conversation by the way. I am just here giving the real facts about the other side of the story (masonry heaters). I used to teach rocket stove building workshops, I just didn't like making up excuses for why they legally couldn't be built in most area's because there is no ASTM for them and they are not in the IRC so officials have issues with them. Plus they are still kinda experimental and will smoke back on you on the wrong day. A properly designed and constructed masonry heater will never smoke back on you once the draft is established. Yes, some clients might get some smoke back in the beginning of a fire IF they did not have the draft originally established. If you are having a fire 1x per day you should never have any issues with draft unless the temperature differential from outside to inside is not that great. Your not going to get a great draft if the inside temperature in 68º and your outside is 50º. Once a fire is going in a MH you should never get any smoke back if it was designed properly.
Eric

Hey Eric,

How can I get a hold of you, off the forum?

Thanks,
alex

Yes, please feel free to contact me personally.
Eric Moshier
www.solidrockmasonry.com
email eric@solidrockmasonry.com
218-343-2978

In a constantly cold climate I'd go with a masonry stove. The rocket mass heater bell is to get heat out quick. You don't want that, you want steady output. I built a "Russian" stove (here in Kentucky) with the help of a professional mason for under $1000. Got Basilio Lepuschenko's "Complete Plans and Instructions for Construction and Operation of a Masonry Stove" from Maine Wood Heat. (no longer available) Not quite complete even if it's in the title. Haven't moved into the house yet so can't comment first hand on performance.