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"Why don't you heat with a rocket stove?"

Rocket stove construction"Have you looked into permies.com and the rocket mass stove that is advocated there?  They talk about how damping a fire down makes the stove less efficient.  And their design lets it burn hot but slowly release the heat."

--- Phil, in response to yesterday's post


We actually get this question a lot, so I thought I'd answer in a post so I can point later readers here.  For those who aren't familiar with rocket stoves, they were developed as an efficient cook stove for countries where folks still largely heat their food with wood.  The design channels all of a fire's heat into a very specific area around a pot and uses preheating of the combustion air and insulation to achieve high efficiency with low cost materials.  One of these days, we may build a rocket stove for summer cooking, but since I spend so much time processing all of our homegrown produce, I don't think I'd have the patience to use a higher work stove at the moment.

Efficient wood stove produces no smokeOf course, that's not what Phil was talking about --- he wanted to know why we don't heat our home with a rocket stove.  While I don't have the data to back this up, I suspect that our scientifically designed, high efficiency wood stove is a more effective space heater than any homemade rocket stove we could come up with.  Our little Jotul uses the same preheating and insulation concepts as the rocket stove, and I can attest to the fact that the smoke coming out the chimney is usually completely clear as long as I'm burning dry wood.  We also burn a fraction of the wood our neighbors do.

On the other hand, Phil is completely correct that you get more efficiency from any fire if you burn it hot rather than damping it down --- that's why we chose a small wood stove that fits our small space and burns little chunks of wood on "high" all day.  However, heating with a wood stove overnight requires you to damp the stove down (unless you buy a pellet stove, which doesn't seem very sustainable to me).  A rocket stove would be a very bad option for overnight heating since the ones I've seen require you to feed small pieces of wood into the stove very frequently --- I prefer to damp her down and sleep.

Rocket mass heaterWhat does make sense for overnight wood heating is adding more thermal mass around any kind of stove.  This is how the rocket mass stove (the heating version) works --- a huge mass of masonry stores heat while the stove is running during the day, then radiates that warmth back into the room when the stove burns down.  Our trailer has weight restrictions, so we can't go overboard with massive cob-type stove surrounds the way some folks do, but one of these days I do plan to tile the living room floor to capture the great passive solar heat coming in our south-facing windows on winter days.  Our slow but sure progress on insulating our space will also help.

Our chicken waterer is the POOP-free alternative to traditional, filthy waterers.


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When I found out about Rocket stoves I also thought the same about them compared to my Wood stove. I don't see how a rocket stove could keep up with my wood stove on extended overnight burns. I can average 10 hours on good seasoned hardwood. I wouldn't want to keep on feeding the rocket stove all night.
Comment by Marco Tue Nov 27 08:38:26 2012
We are very much looking forward to the installation of a new wood stove in our trailer next weekend. It will be nice not to have to depend on expensive gas or unreliable electricity anymore. We lost power for five days during hurricane Sandy, and we frequently lose power during heavy snowstorms. I can see how a rocket stove might be ideal in some living situations for some folks but a wood stove makes more sense for us mobile home dwellers.
Comment by Monica Tue Nov 27 08:58:13 2012

A small masonry heater is around 1750 lb. If that is too much for your trailer's frame, you can get around that by putting a foundation for it (e.g. a slab of concrete) directly on the ground under your trailer. On that foundation you can use e.g. cinderblocks to built support "towers" in between the steel beams of the trailer's frame to carry the weight of the masonry heater.

This is more or less the same as how fireplaces used to be built in wooden houses.

The German wikipedia page for the Kachelofen has some interesting performance graphs.

Comment by Roland_Smith Tue Nov 27 13:58:38 2012
mother earth news the amazing $500 woodstove that you can build for $35 or less
Comment by Anonymous Tue Nov 27 15:19:49 2012

Hey I was referenced in a homesteading blog! Just for full disclosure, I have never owned used or seen(in person)one of these Rocket mass heater stoves, but I have used regular wood stove and built and used one of the cook type rocket stoves as illustrated at the top of the posting.

It is amazing with the cook stoves how much energy is in a few twigs. They light quickly, and once heated up are completely smoke free. It will bring a small pot of water to a boil in very few minutes. We take it camping with us to cook with because it is less hastle than a Coleman gas stove. But it is not a "gather round the campfire" thing, the heat is condensed on the pot. So it is really hot or you don't feel the heat. Not good for warming your cold backside.

But as Anna mentioned, adding mass makes a HUGE difference. They (Ernie and Erica) at Permies http://www.richsoil.com/rocket-stove-mass-heater.jsp claim to build one fire of a small bundle of sticks, and it keeps thier small home warm for days. They have videos and diagrams, including the one that Anna used, and it will explain the Rocket Mass Heater concept better than I could. It looks incredible.

I can see that the weight would be too much for the floor of a mobile home. It would require substantial additional support to do it. But if you would put all that mass under the floor to support the mass on the floor, why not move the heater into the crawl space under the house. This would save space in the house and keep dirt from the sticks and ashes out of the house, if the fill tube was outside.

I just wanted to say that I am so inspired by this blog, it is a true roadmap for freedom.

Sorry for being so long winded.

Comment by Phil Sat Dec 1 14:19:03 2012
...in the world are you living in a trailer?? The amount of money you've lost with just the heat alone would've enabled you to build a tight and efficient home with a concrete slab and in-slab heating that would still be working inexpensively.
Comment by tex Fri Jan 3 02:34:00 2014
Tex --- You can read the long answer in Trailersteading. The short version is --- we hate debt, and we figure we spend a lot less on extra heat for our trailer than we would on a mortgage for a traditional home. Whenever we have extra cash, we can weatherize the trailer and cut back on our heating bills drastically, while it takes a lot more cash to cut back on mortgage bills.
Comment by anna Fri Jan 3 09:31:23 2014