Rocket Mass Heaters

A rocket mass heater is a clean-burning, high-performance burner usually put together using a majority of recycled and/or natural materials, such as cob. Owners claim an 80-90% reduction in wood usage compared to heating the same space with a metal wood stove.

Rocket Mass Heaters: The Basics

As opposed to the masonry heater, which requires some advanced masonry skills, the rocket mass heater can be built by any enthusiast with basic masonry and engineering abilities. The only problem with this project is difficulty in getting a building permit, because basically not many officials know what a rocket heater is.

The exception is Portland, Oregon, which has a building code for rocket mass heaters, thanks to Ernie and Erica Wisner, who share some hints on how to acquire a permit on their site. Many communities do have building codes and give permits for masonry heaters, so you might need to treat your rocket heater as a masonry heater. Be cautioned, that without a permit, you may void your fire insurance policy.

Rocket Mass Heaters: How They Work

The rocket mass heater works on similar properties as a masonry heater. A fast, high heat and oxygen-fed fire burn up the volatile gases and particulates, leaving very little pollution, and turning almost all the fuel into energy. A bit of smoke is released during the first minutes of a fire, until the temperature in the chamber is hot enough to burn the combustion gases as well as the wood.

The major difference between a masonry heater and a rocket, is that the rocket stove has an insulated J- or L- shaped combustion chamber that forces the fire to burn horizontally. The fire then hits a 90 degree angle at the end of the chamber which causes a strong turbulence to rise up the insulated heat riser, creating a strong draft that feeds the intensity of the fire.

The heat riser sits inside a barrel or larger secondary chamber which extends a couple of inches above the inner riser. The hot rising gases hit the top of the secondary chamber, give off some of their heat and then fall down the larger chamber’s sides. The exhaust is then directed through flue piping, usually set within a bench, which will absorb the last vestiges of heat.

Today’s rocket heaters often employ cob, but there is no reason why you can’t build a masonry bench of brick, stone or tile. The final flue gas that escapes the exit is basically water vapor, as hydrogen during combustion turns into water vapour.

Small pieces of wood, basically trimmings from one’s yard, can be used to fuel the heater. The spaces between the small pieces of wood allows more draft into the combustion chamber, helping to fuel a fast, hot fire.

20 Eye-Catching Rocket Mass Heaters: Examples and Plans

1) Exposed Drum


Rocket mass heater. Leaving the drum exposed allows immediate heat to enter the room. Covering the barrel with a natural surface of cob slows down the instant heat and holds heat for slower release. Found at

2) Straw Bale Home


Rocket Mass Heater in a straw bale home in France by Bec Touvière. Courses given once a year in France. Great video of the process at bottom of page here:

3) Bioconstruyendo Rocket Mass Heater


Rocket mass heater, built during a Bioconstruyendo held in February, 2010 in Patagonia, Argentina, in a straw bale and adobe cabin. Visit for this picture.

4) Textured Heater

This heater has a great rustic vibe. The slight texture in the rocket mass heater is a nice touch.

5) White Rocket Mass Heater

Rocket Mass Heater by Juured in Estonia. Their site has more information.

6) Heater With Rock


Rocket Mass Heater by Ernie and Erica Wisner. Plans for sale here:

More On How Rocket Mass Heaters Work


The combustion chamber runs horizontally, the flames and gases hit a 90 degree angle and then throw off a lot of strong turbulence, which helps intensify the heat and create draft, or a rocket effect up the heat riser. The heat riser is usually a smaller pipe set within a larger pipe, the inner heat riser needs to be insulated as that creates a heat differential which again increases draft.

This heat riser is then usually set within a 55 gallon barrel, with the top exposed to give off instant heat, but there is no reason it could not be set within masonry. (See resource below.) The barrel’s lower half is often covered in cob, to store the stove’s heat and allow the heat to radiate slowly.

Rocket heaters need a heat riser that is at least twice as tall as the burn tunnel is long. From: Rocket Mass Heaters by Ianto Evans, Leslie Jackson.

7) Modern-Styled Heater


Rocket mass heater and cooktop in Brussels. Great design! Brick veneer and must be a refractory cement counter top. This photograph is from


Wood goes into feed to right of the sink. Cooktop is to right of the feed. See the inner workings here:

8) Cabin Heater


Rocket mass heater by Ernie and Erica. This heater was built for a cabin. More information can be found at

9) Stove In The Shamen Center


Rocket mass heater in a Shamen center in France. From “Rocket stoves, wood fires and mass heaters”. Visit for additional information.

10) Heater From Estonia

Rocket Mass Heater by Juured in Estonia. For more stories and pictures of cob, go to Juured’s website.

11) Cob House Heater

You can see how they used cob to seal the barrel.

12) Heater At A Cottage Home


Rocket mass heater in Cob Cottage, Coquille, Oregon, the home of the creator of the Rocket Mass Heater, Ianto Evans.

13) Cooking Rocket Mass Heater


Rocket mass heater mostly used for cooking as it is in the highlands of Guatemala. Find more on this story at

14) Large Heater


Mass Heater by This is only one example they have on their website.

15) Masonry Heater


This is a masonry mass heater but looks like a nice start off point for a design of a rocket mass heater. Photo from

16) Antique Stove


An antique stove was surrounded in cob. The wood loads on the right side, there is a heated bench behind. By Ernie and Erica Wisner, more photos:

17) Heater Without A Barrel


Rocket mass heater with a cooktop. The heat riser does not have to be a barrel, but can be built from masonry. This photo was originally found at “”.

18) Reading Corner

Rocket stove heaters are great for lounging on during cold winter months. If placed in a corner, you can create your own heated reading nook!

19) Lounging Rocket Mass Heater


Rocket mass heater by expert Kirk “Donkey” Mobert,, Information and photographs can be found on

Rocket Mass Heater Diagram

rocketThis diagram was actually from a forum, to view the whole conversation visit

20) The Dragon Heater

dragon heater

Dragon Heater’s 6″ powder coated metal rocket heater. Kit includes everything but the 55 gallon barrel and the perlite. It can be operated on its own or connected to thermal mass storage. Inside the red box is a 6″ Dragon Burner. A square feed tube and 2″ round air intake. The barrel has been painted with Stove Bright Hi-temp paint in black metallic. Available in 4 colors, textured black, copper vein, silver vein, and red. $1450. Go to for more information.

Rocket Mass Heater How-To Videos

How To Build A Rocket Mass Heater

Metal Heaters

The Best Books About Rocket Mass Heaters


Written by Keiren

Keiren is an artist who lives in New York City. A lover of animals, nature, science & green building. Keiren originally founded Inspiration Green in 2007, which merged with Insteading in 2016.


Leave a Reply
  1. These look so stylish! And surely they’re pretty efficient as well, as gas prices are going up, this is certainly a good alternative!

  2. Hi Guys, hello from South Africa, I looking for some help in building a rocket heater here but cant afford the book 🙁 Need to know a couple of details etc. Anybody out there?



  3. very encouraging and informative .planing on using some of the ideas in my 30’x90′ poly tunnel will send u pictures if u guys would love that one love

  4. What’s the the smallest size RMH that can be used and still be efficient, I’m trying to make as small of a square foot design or small foot print As possible. Can I make it tall and thin? In maybe 3×4 foot area?

  5. Good write-up, I am regular visitor of one’s web site, maintain up the excellent operate, and It’s going to be a regular visitor for a lengthy time.

  6. My mother-in-law walks naked in the house now that I finished their mass heater. The central air just is not as warm feeling, it is dry feeling. Also it is cheaper to heat to a higher temp, and that is why that wrinkled old bag has gone nude like in the old country.

  7. I’m curious if there is any way to somehow add an out mesh like screen about 3-5 inches away from the exposed barrel that would help keep kids/pets from touching it and getting burned. with some sort of small latch door so you can still get to the barrel if need be. I have a cat and some day would like to add kids to the mix. ..I’m just not sure if the exposed areas will be safe enough.

  8. Hi Lauren, Or you could cover most of the barrel in cob, like the second photo from the top. And then put some woobly piece of metal atop so the cat will quickly learn not to jump up. Or the mesh as you say….I will keep my eye out for any examples. Best!

  9. I love rocket heaters. Right now I only have an iron parlor stove for my little cottage but one day I want one of these. I’ve never seen so much eye candy on one web page before. Beautiful heaters!

  10. This is my first discussion board entry at this point.! I am pleased to be obtaining associated in this article and since I am new to discussion board neighborhood, I really feel occasionally, that I’ve to understand a whole lot, believe you fellas have patient on me.Thank you see you guys

  11. Hallo,

    I like so much this rockets and I want to make one by my self. I have some questions if it is possible to get answers:

    1. Can I use the old vent to take the smoke out. It is about 6 m long. And I intend to make a 3 m long bench.

    2. The hole for in take air it is so necessary? In Ianto Evans book I did not see mentioned. If yes it can be a regular small door? I can use the same kind of door for the ash cleaner place?

    3.The third door it should be on the and of the bench? It can be the same with the other ones? Or should be something with very good close up?

  12. I have a hot water boiler that feeds baseboard units. I want to remove the unit and build a rocket stove from a hot water tank to heat the water instead. Can I connect the water lines (cold, hot, return) to the water tank?

  13. Hi, Please check out the forum on rocket stoves…so much info there and so many who can definitely answer your questions!

  14. I am building a webpage about this solution for the problems we have with natural gas in the north of Holland.

    More and more earthquakes are breaking houses, but nobody is thinking of a soultion.

    Rocketstoves are. Keep up the good work.

  15. Outdoor heaters are the only way to provide warmth, and the best way of increasing comfort for outdoor

    social areas of any size.

  16. Hi! Very interested in this technology. For home use it would seem that the home would provide combust ale air thereby decreasing overall efficiency. Is there a system that uses outside,air?,would this increase efficiency? Thanks in advance,

  17. The most attractive examples, I think, are finished in white.

    What exactly is the white finish coat on those RMH’s?

    Thanks. I really enjoyed this page!

  18. The picture labelled ‘Rocket mass heater in a cob cottage in Eugene, Oregon’ is actually located at Cob Cottage in Coquille, Oregon and is the home of the creator of the Rocket Mass Heater, Ianto Evans.

  19. I’m confused, these do nothing significantly different than any well-designed masonry heater and I don’t see that they require any less masonry skill to create?

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