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.
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Mid December our miniature 12,5cm / 4.9inch CSA #RocketMassHeater #RMH finally got finished and we could switch off our stinking gas heater. Now this #dragon is the only heat source in the house, gets fired twice a day (morning / night) and keeps us warm even through the tough days around freezing we had in our mild mediterranean, warm temperate climate. #permaculture
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 permaculturedesign.fr.
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: permaculturedesign.fr
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 www.firespeaking.com 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: ernieanderica.info/shop
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 flickriver.com.
Wood goes into feed to right of the sink. Cooktop is to right of the feed. See the inner workings here: flickriver.com
8) Cabin Heater
Rocket mass heater by Ernie and Erica. This heater was built for a cabin. More information can be found at ernieanderica.blogspot.com.
9) Stove In The Shamen Center
Rocket mass heater in a Shamen center in France. From “Rocket stoves, wood fires and mass heaters”. Visit ecologie-pratique.org for additional information.
10) Heater From Estonia
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 joachim2010.blogspot.com.
14) Large Heater
Mass Heater by terre-et-flammes.fr. 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 poeles-eco-09.com.
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: plus.google.com
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 “marquedeposee.over-blog.com/article-p1220438-jpg-103910105.html”.
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 Diagram
This diagram was actually from a forum, to view the whole conversation visit systemed.fr.
20) The 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 www.dragonheaters.com for more information.
Rocket Mass Heater How-To Videos
How To Build A Rocket Mass Heater
- Very active forum: permies.com
- Another forum: donkey32.proboards.com
- Plans: ernieanderica.info/shop
- Permit/Building Code Issues: ernieanderica.info/rocketmassheaterpermit
- Picture Guide: outdoorhub.com
- Design Tool for measurements for stove: rocketstove.org
- RMH with bread oven, step by step photos: es-cargo.qc.ca
- Nice heater here: www.mayacreek.org
- Typical exhaust system: midwestpermaculture.com
- Understanding the bell: stove.ru
- More on the bell design: handprintpress.com
- Kits: dragonheaters.com
- Step by step photos of a masonry rocket mass heater: www.mha-net.org
- Round masonry rocket mass heater: mha-net.org
The Best Books About Rocket Mass Heaters
- Rocket Mass Heaters by Ianto Evans, Leslie Jackson.
- The Rocket Mass Heater Builder’s Guide: Complete Step-by-Step Construction, Maintenance and Troubleshooting by Erica Wisner and Ernie Wisner.
- Lessons from Our Rocket Mass Heater: Tips, lessons and resources from our build by Ray Dudley and Randi Dudley.
- Clean rocket stoves for developing countries, yeah! www.aprovecho.org