Rocket Mass Heaters

When I first moved to Idaho, I spent the first few years on a rural mountain property in the Selkirks in a wall tent.

I had an abundance of heat inside of my wall tent, even in the dead of winter, because I built myself a ROCKET MASS HEATER.  I burned about 95% of a single cord of wood that winter.  Not quite a single cord.  Any form of heating I have dealt with since, whether wood heat from standard stoves, electric, cheap-oil, etc, has proved decisively inferior.  Solar and geothermal are the only superior forms of heat~ yet in our cold winter climate, they by themselves are not fully sufficient.  Sound design can unify all of these and keep us comfortably warm each year at virtually no cost with no waste.

Everyone I’ve told about my experience with RMH’s has wanted to know more.  I am prepared to consult and help people with the construction of the most difficult parts of these fabulous, efficient, work-saving, custom masonry stoves.  I’m qualified, and I’ve got the experience. These things work for real.  Browse this webpage, check the links, or send a casual inquiry for more info.  It is very nice to prepare wood for a season when you’re not scrambling to get so much of it because of a wasteful stove.  I believe this technology is fundamentally valuable if not only because of how much money and work it saves people in putting up firewood.

 

 

WHAT ARE ROCKET MASS HEATERS??

RMH’s, while pulling from native technologies 5000 years old, were originally invented in Oregon early 21st century using exclusively cob.  Today, there are many in existence using a good variety of materials. They are something of a fusion between ancient indigenous practice making channeled fires in burrowing prairie mammal holes and medieval European masonry stoves- an elegant combination of fluid mechanics and thermodynamics.  They utilize an insulated, vertical masonry burn chamber that then routes hot exhaust gas through a thermal mass to both burn efficiently getting the most heat out of less wood and store the heat. 

Here is an introductory video I made of the first system I built, detailing construction and performance:

 

I have worked on custom masonry stoves over the summer of 16′ under the tutelage of the people who wrote this book and compiled the resources found

on this page.

I also worked that summer editing footage, and was on the team that made

these DVDS.

 That online web forum has MANY discussions about these, and likely has answers to your question.  If you were serious enough and had the time to research it, there should be nearly all the technical info you need to build one yourself. 

 

 

Sample RMH Design (not a build-plan)

 

 

OTHER COMMENTS

The bench can be as short as you like.  It has limits on how long you can make it, but in the name of resiliency you don’t want to push the limit too far.  That said, these can get big.  A smaller 6 in duct system wouldn’t be able to fit in a space smaller than 100 SF.

The longer the amount of ducting, the more potential for heat storage but the less reliably it will draft. This can be mitigated in a number of ways- switch bevel, chimney parallel to bell. Generally speaking, a 6 inch system is good for 15-20 feet and an 8 inch is good for 20-30 feet.  Materials have not been innovated to handle the temperatures of a 10 inch system.

Their performance, when well built, is well documented, and I believe they are the premiere form of cheap, clean, renewable heat for our area. An rmh and an old wood cook stove is a purely luxurious combination. But they are not for everyone. 

I do not know of anyone who is sorry to have tried them out after having built a legit one. 

YouTube is loaded with crap videos about these. While there are a few decent accounts that give reasonable reviews, I wouldn’t waste too much time researching them there.

My first independently built one, by purely myself, took about a solid work week to build once materials were acquired. I wouldn’t budget less time for them as they are rather large features.

Build them during warm season- late spring to mid autumn is fine.  If mass will be wet for whatever reason as you assemble it, let it dry before adorning it with cushions, blankets, etc. Take safety precautions with dust, etc.

Caring for an RMH means vacuuming fly ash out of it through clean out ports once every year or two, and perhaps a simple re-mortaring of something (particularly around where air is flowing into the wood feed and it heats up really hot and then cools down) every now and then.

 

IS A ROCKET MASS HEATER RIGHT FOR YOU?

Future societies will have rocket fire technology much more integrated. When doomsday comes out, you don’t want to need a chainsaw. A bowsaw will cut easily the size fuel you need from coppice woodlots that maintain their fertility generation upon generation like the systems our ancestors in Europe used to rely on.  RMHs are no silver bullet and do not work in all cases.  I would not want to replace every single wood stove with one.  But for MANY people’s situations, dare I suggest a majority of wood-burners?  The future will tell.

No lies or delusions. Reach out with questions.  I have offered advice for free during office hours to people to see if an RMH would be right for them.  There is opportunity here.  I would be willing to help out with design or masonry work to greater extents for hire.  They really are nice, and save energy, time, money and work in the long run, for certain circumstances.  Send a message if you’re interested.


If you use any kind of wood burning heat, consider measuring quantities presented in the following form.  

Wood Heat Data Analysis


 

Here is a simple brick J-tube, the most fundamental and simple unit of a rocket stove.

 


See attached handout for construction details, tools needed, PROS vs CONS checklist, etc.

RMH INFO Handout


 

RESOURCE AQUISITON

At Pro x – 

Portland cement 6-60$

Black stove pipe – straights 9-15$

Caps 12-15$

Bends 10-12$

T’s 20$

Manifold pieces 7-10$

Roof caps 7-15$

Gaskets 10-16$

Fireplace cement 3-5$

 

BONUS – 

Built at virtually zero cost, this small rocket stove uses mere handfuls of scrap/twig wood to replace the need for conventional gas/electric burners.

 

 

More Info: Google them!  People are getting more and more into them.  Forums on Permies.  Schematics adapted from linked content above.