Rocket Mass Heaters

Efficiency is a big deal in everything we do.  Heating a home with oil or a fireplace is not terribly efficient though.  Definitely not efficient enough for living off the grid on our homestead.  So what should we do instead? Build a rocket mass heater of course!

What is a rocket mass heater?  A rocket mass heater is a wood burning heater that burns sideways sending smoke into a heat riser which then sends the smoke out into a  bench and finally the exhaust lets out around 90 degrees.  I know that it sounds a little funny, but check out the picture below and I’ll try to explain it better.


The wood to burn goes into a small opening and is gravity fed into the burn chamber.  The “rocket” part of the stove is the super insulated heat riser.  The insulation causes it to burn hotter and more fully.  The super efficient burn is what causes the fire to suck in sideways towards the heat riser.  This does mean that you have to get the fire going before it is efficient.  All that means is that you will get some smoke back while you are starting the fire.  All this heat is then pushed out into a tube which is located inside a large thermal mass.  Often the thermal mass is a cob bench.  The thermal mass absorbs the heat, stores it, and slowly releases it into your home.  The benches only reach about 100 degrees so they are perfect for sitting on to warm yourself up, not burn you.  Once the heat running through the thermal mass finally reaches the exhaust point, it has cooled off to just above room temperature.

The reason this whole set up is so efficient is for a few reasons.  You get a complete burn. There is no wood wasted in ashes or creosote.  That also means less need to clean the system.  The burn is hotter than a standard wood stove so you are getting more heat from the system.  The heat is then absorbed into the system so all the heat that would normally just escape through the chimney is being stored for use in your home.  The actual exhaust is already mostly cooled off.  Basically, there is nothing wasted.

This is the most efficient heating I have found so far.  I plan on building a home with passive solar heating, but I will likely need something extra and this should do the trick.  So now to build a rocket mass stove to see how well that works for me.  A simpler practice project for us to start on.

Here are some links for more info:

Midwest Permaculture

Rich Soil

Inspiration Green

And now, check out this T-shirt!

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I want to introduce the rocket stove/biomass latent heating system in Central Asia where I work. Can help me locate any crafters and examples within a 2-4 hour drive of the Hartford CT area?

There isn’t much out there that I know of. Try contacting NOFGA maybe? They are more organic farming but may be aware of some permaculture type stuff. We left that area partially because of the lack of anything permaculture in the area. Umass has a permaculture garden, maybe they could direct you better. Sorry I’m not much help, but there isn’t much there either. Good luck! Let me know how you make out.

Everything here is so suburbanized and zoned, so we are trying to find somebody, a sub-contractor possibly, who is building rocket mass walls that esthetically would fit in a hopelessly midwestern subdivision. ?

Many places do not allow rocket mass heaters at this point. They don’t fit into building laws and regulations so it can be difficult to find a contractor to build them. You may have to do the building yourself. Look around and see if there are any natural builders near you. This is your best bet. Maybe cob builders or something like that. You may get lucky and find a mason who could do one of these. Many masons don’t even know they exist, but if you could find someone who is interested, they may be willing to learn. Where do you live? I could check it out.

We finished our rocket mass in our greenhouse just in time for this winter. It is awesome! I am so glad I took the time to research, plan, and build it. The most efficient heating system I know of. We are in the Mid-Atlantic Region. Thanks for the info.

No problem! I can’t wait to get ours going. I have yet to find any other system that looks like it could even come close in efficiency. Maybe the masonry heater, but that seems like pretty close to the same concept.


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