Tiny mass heater for small homes.

This is not A rocket anything. This is not made with cob. It is a tiny (by mass heater standards) mass heater. It tries to do everything.... heat your house, cook your meals, heat your water and even work with the door open as a fire place for ambiance. It is designed to burn the wood completely and smokeless. Disclaimer... I am not suggesting it meets any or all of these objectives. I would also point out that this is a first prototype of a design that will get better as the maker works out what problems there may be. The plans have been posted free to download as well (such as they are). The current prototype is single skin for testing but is meant to be finished with an outer skin. The outer skin could be cob, but I think they are planning compressed earth blocks. I have also seen cement pavers used.

http://www.firespeaking.com/media/articles/the-cabin-stove/

In mass heaters a core (inner skin) and outer skin are normally used. This is both to add more mass as well as to make a second smoke seal to keep things like CO2 out of the house. The RMH has lots of cob to perform this function. In either case (or with an iron stove for that matter) a CO2 detector is cheap insurance against loss of life.

Also, (and I have left a link to it before, I think) there is a cob add-on to an already installed iron stove to make it work more like a mass heater. It even has an oven in it.

http://www.handprintpress.com/ovens/bring-in-the-mud/

I like that design.  I think that I would lean more towards one of these than a Rocket Mass heater.
Personal preference...

Thanks for sharing that.

Shawn Bell wrote:
I like that design.  I think that I would lean more towards one of these than a Rocket Mass heater.
Personal preference...

Thanks for sharing that.

It is built from used firebrick... I would guess that one of these could be built cheaply as a RMH if used firebrick was to be had free. Making the doors would be not too hard for someone who welds. The most expensive part would be the flue pipe out the top to meet code. For a one off project, a cut-off saw would with a masonry blade would be enough to get the job done. The RMH requires no tools or previous skills and if built from scrounged parts can be cheap and more doable for those with less tools/skills.

Really, that should be, those with other skills than construction. I can build lots of stuff... but my garden is less successful.... just as an example.

Hello This is a very nice design and quite beautiful, i was wondering about its wood consumption though, one of the main points to a RMH to me at least is the amount of wood it uses. is this design also as frugal on wood consumption.?

Cyric30 wrote:
Hello This is a very nice design and quite beautiful, i was wondering about its wood consumption though, one of the main points to a RMH to me at least is the amount of wood it uses. is this design also as frugal on wood consumption.?

It would probably be best for the designer to answer this. He can be reached by email from the article linked to in the first post on the thread.

My general answer   Is that there are too many variables to tell. Even from one RMH to the next there are differences and for that matter, two identical RMHs in two different houses would have different results.

Both heaters are mass operated and so the first comparison would have to be a RMH of the same mass (or same heat storage capacity) and used in the same house and climate. This heater is designed for: a) a small house. b) a warmer location such as the PNW on the coast..... where even though it is raining and I work outside... I am wearing shorts and a t-shirt (49.5 deg. N). A very cold night will see -10C (+14F) at the lowest (in January).

The next thing to look at... is that this is designed by a mason (member of MHA) who thinks in terms of permits and will not design for the RMH trick of exhausting with a head height horizontal pipe. So the comparable RMH would also have to be built for permit and a chimney.

So, my guess, is that this stove would preform about the same as a RMH with a bench of similar mass and chimney in the same house. Maybe better as I personally think the flue gas routing will extract more heat into the mass than a RMH of the same size. Most RMHs rely on a long heat extraction pipe for their effectiveness. The cabin this heater is designed for would not want to give up the room required for a RMH to work as well.

Really, a RMH is a type of masonry heater. Its strong points being that it can (for some people) be much cheaper to build and it can be built easily by an owner who has no masonry skills. An owner who is willing to learn those skills may be able to come pretty close price wise to a RMH with a masonry unit. However, many places require a certified mason to do the work for a permit to be signed off. There have been too many houses burnt down from wood burning appliances for it to be otherwise. (even though most fires have probably been iron wood stoves and not masonry heaters)

This heater is nice in that it combines a number of things many people are looking for. It is small. It has a cook top at a nice height. It heats water. It uses mass to store heat for after the fire is out. It burns cleanly and makes good use of the fuel. In a cabin in some places, it would be exempt from some wood burning regulations because it could be the only or at least regular use cooking appliance. There doesn't seem to be an oven there but, I suspect the firebox would make a great "retained heat" oven for cooking bread in (or other food...  I mention bread because it wants the highest heat) after the fire has gone out. One last advantage over a RMH is that this is a batch burning device... the whole wood load is put in and the fire is started (top down please) and when it is fully burned the heater is as warm as it should get. A RMH must be fed once in a while till it gets to max temp. It would depend on your point of view if this is a plus or a minus.

Here I am working on a RMH and now talking myself out of it

That is much like a Russian Masonry Heater that has a long history. Before I saw the rocket stove concept several years ago, I'd been planning to build Russian MH for a lot of years.  Searched Russian MH and got this link.

http://www.firecrest-fireplaces.com/Products-Russian.htm

I think that there is probably little difference in the amount of wood used, or in the cleanliness of burn, between a well designed masonry heater and a rocket MH. I think that for me a variation of the rocket MH is better. There is a lot of similarities in the rocket MH and the Russian MH.

Leave it to Aprovecho to lay claim to inventing the Russian Masonry Heater. I like their design with the oven.. It wouldn't be all that hard to make a rocket MH that had a stove top and oven - the barrel isn't the only way to build a rocket MH - just seems to be the common (inexpensive) way to go.

ronie wrote:
That is much like a Russian Masonry Heater that has a long history. Before I saw the rocket stove concept several years ago, I'd been planning to build Russian MH for a lot of years.  Searched Russian MH and got this link.

http://www.firecrest-fireplaces.com/Products-Russian.htm

Some similarities yes... however, I would say this design is different than any of the Russian (or Finnish, or whatever) heaters. There is one Russian concept in this and that is the idea of multi-use. The Teplushka uses the closest flue path to this small stove, but is big enough for a family to sleep on top.

There is a lot of similarities in the rocket MH and the Russian MH.

Yes, the main difference is the batch burn as compared to a continuous feed. The RMH is based on the masonry heaters from Europe... The more one looks the more similarities one finds.... but is designed to use found materials. Having said that, the old Russian Peasant stoves.... actually ovens.... were often built from clay from the surrounding land... permits hadn't been thought of (and yet somehow mankind survived).

Leave it to Aprovecho to lay claim to inventing the Russian Masonry Heater.

Say what? I didn't get that from it at all. Are we reading the same page? Even the title says "A Small Masonry Heater", clearly saying this is one of something that already exists. Farther down "The challenge of the design of the Cabin Stove was to come up with something that was very compact but also still resembled and functioned like a masonry heater." This clearly points to it's roots... the European masonry heater.

I like their design with the oven.. It wouldn't be all that hard to make a rocket MH that had a stove top and oven - the barrel isn't the only way to build a rocket MH - just seems to be the common (inexpensive) way to go.

Actually, this design doesn't have an oven, but like all good masonry heaters, the firebox should hold its heat long enough to be used as one. Good permaculture idea, getting more than one use from something.

Something I have noticed as I have looked through some of the tiny houses both in the thread on this site and in other places... not too many RMH in there. They tend to take up a lot of room... they are fine for 600sqft cottage, but I think once that drops to 200 sqft or maybe even a bit bigger... it becomes too much of a one use space. Most of the tiny houses I have seen that wish a mass heater, start with an iron stove and add lots of brick around that and it's flue... but that mass is mostly vertical... small footprint. There is also a niche where a large mass heater is maybe not so good. The Russian heaters are made in response to Siberia. Cold, long winters. This is made for the coastal regions... in particular West coast. We could survive here with no heat (not comfortably but our unheated basement sits around 50F at the coldest time of year... survivable with proper clothing). A small stove like this would be a good match. It's cooktop is lower than a RMH barrel top... nice. The RMH needs that height to work right (take the smoke out of the house not in). Attempts to add an oven to a RMH have both been less than trivial and as I recall, not good for much more than a warming oven. This one could work as the only cooking appliance in the house... for a 150sqft house? nice.

I don't think this would be great in Missoula for example... A few dogs (or dog heating pads... or was that chicken heaters?) might be needed to keep a man warm as well as this stove  Though those up Sugar Mountain in Vermont might not agree with that as they went days at a time with no fire in their small home. Lot of variables... and a different heater to fit each use. I think I will continue on my RMH project... if for no other reason than it will cost almost nothing and I have a few ideas I want to try... yes an oven even.

I think the tiny house folks should look into putting the mass below floor level instead of in the room.

ronie wrote:
I think the tiny house folks should look into putting the mass below floor level instead of in the room.

Some do... some can't. No such thing as one size fits all. For a good example of under the floor, see this thread:

https://permies.com/permaculture-forums/5937_0/alternative-energy/rocket-mass-floor-heater-finally-completed-and-it-works

Even the fire hole has been moved outside.... But look at what they had to do to make it work... No cooking on top. (without a ladder)

The rocket stove that the RMH is based on is older than the European masonry heaters...What makes today's versions interesting are the refinements. A close look at the "standard" contraflow masonry heater shows something very close to the RMH... the difference is mostly in feed..... and price. I get the idea (I could be wrong) that the thinking that brought about the RMH went something like this:

Wow, those masonry heaters really work great, they would complement this cob house really well.... It would cost how much!!!  Hmmm, well cob is a lot like brick what if we packed it around a metal form, we have lots of junk hanging around....

  Len, if you have any plans which include used firebrick or other used brick and you're planning a trip to Victoria give me a call. I seldom sell the firebrick and quite often when I'm on a tight time schedule other brick goes to waste as well. Sometimes there are good ceramic flues as well. Stop by and load up for free. Dale: 250-588-3366

dale hodgins wrote:
   Len, if you have any plans which include used firebrick or other used brick and you're planning a trip to Victoria give me a call. I seldom sell the firebrick and quite often when I'm on a tight time schedule other brick goes to waste as well. Sometimes there are good ceramic flues as well. Stop by and load up for free. Dale: 250-588-3366

Funny, since we have moved from Surrey to Courtenay in 2006, we have been to Naniamo lots, even to Tofino a few times, but not Victoria yet... But yeah, I would have to be going there anyway to make free at least as cheap as new   Fuel builds up quick... Naniamo costs me about $50 round trip (A little less maybe).

When is the wooden boat show? 

I like what this man has done.

www.geopathfinder.com/9597.html

Katee wrote:
I like what this man has done.

www.geopathfinder.com/9597.html

That was one of the designs I was referring to above, here is another smaller one... this article doesn't show all the mass though.

http://flashweb.com/blog/2009/03/16th-cord-of-wood.html

The RMH is a good heater. However it is not for everyone. For some people it is how it looks, for others the materials are hard to find, some people want to do all their cooking on it and find the barrel too high for comfort (not to mention the cob bench you have to reach over).... others need a permit.

The main problem for me with these two stoves, is that they want to be cooking stoves, but have no oven. A heater with a brick firebox can be used as an oven. So the brick heater at the top of the thread could be the "primary" cooking appliance, having both a stove top and an oven. I guess these two could be too, as an oven is not a necessity. The distinction of primary is important in some places as it allows less stringent rules to be applied. I think EPA certification is not required in a primary cooking appliance, but is in a heater. (your mileage may vary.... this may not be true everywhere)

Might be worth checking this link out.... another ubersmall masonry heater.