Rocket Mass Heaters

2 Rocket Mass Heaters © Ianto Evans and Leslie Jackson ROCKET MASS HEATERS: Superefﬁcient Woodstoves YOU Can Build Ianto Evans Leslie Jackson A Cob Cottage Company Publication 2006 - 2012

© Ianto Evans and Leslie Jackson Rocket Mass Heaters 3 This book is obtainable by mail order from Cob Cottage Company Box 942 Coquille, OR 97423 Phone (541) 396-1825 Website: www.cobcottage.com $23 (includes shipping) or USPS money order ($35 for two). Cheques, add $5. This book is also obtainable in .pdf format and in hardcopy from www.rocketstoves.com First Edition Notes: This is a long-overdue book on a unique heating system that will be invaluable and fascinating to any people who want to heat with wood and be comfortable 24 hours a day. Only a handful of people have been pyromaniacal and hardy enough to try to build Rocket Mass Heaters charged by a Rocked Stove. You are now joining that handful. Following further research and feedback from readers, an expanded edition is planned. If you make a substantial contribution to the new edition, we’ll send you two copies when it is published. –August, 2004 Second Edition Notes: Here, since its first printing in 2004, is published the up- dated story of the Rocket Mass Heater for cob buildings, with theories and de- tailed descriptions of how we and people we know have built successful models. It includes improved and expanded drawings. Since its first printing, many of our friends have designed and built their own Rocket Stoves, using this book as their diving board. They appear in this edition with the results of their inventions, experiments and discoveries. We invite and encourage you to test these methods for yourself and use your pyro-wisdom and creativity to come up with your own version, with the caution that this science is speculative because there has been little development of it until now. All illustrations are copyright Ianto Evans or Leslie Jackson, unless otherwise noted. The text is also copyright, but you are welcome to use it in any way you want. We ask that you please acknowledge your source. We just want people to get stoveing and stop supporting the utility corporations. It does help our work if you buy books directly from Cob Cottage Co. or Leslie Jackson. Buy a dozen or a whole case, give them as presents or sell them at gatherings, classes, conferences, etc. It will pay for your firewood. –February, 2006

What this Book is About .................................... 9 Who this Book is For ....................................... 9 The Fine Print .......................................... 9 Cross-section of a Typical Rocket Mass Heater ................ 11 Ianto Knows Why Rocket Stoves ............................ 12 Signiﬁcant Features of Rocket Style Heating Stoves ............. 13 Draft Works the Stove ..................................... 14 Campﬁres ........................................ 14 Chimneys ........................................ 14 Woodstoves ....................................... 14 Rocket Stoves are Different .......................... 15 Combustion and Heat ..................................... 17 How Wood Burns ...................................... 17 The Three T’s ....................................... 18 The Thermal Battery ................................. 18 How Heat Moves ...................................... 19 Radiation ........................................... 19 Convection ......................................... 19 Conduction ......................................... 20 Insulation ........................................... 20 Comfort Through Stored Heat ........................... 21 Step-by-Step Construction ................................. 22 Designing Your Stove and Thermal Battery ................... 23 The Combustion Unit ................................... 23 Directing the Heat...................................... 24 The Thermal Battery ................................. 25 Placing the Pipe ...................................... 25 Sizing Built-in Furniture ............................... 27 Planning the Exit Flue ................................... 27 Materials and Tools You’ll Need ............................. 29 Bricks.. . ............................................ 30 Clay ............................................. 30 Sand ............................................. 31 Barrels ............................................. 31 Stovepipe ........................................... 32 High Temperature Insulation .......................... 33 Insulation Containers ................................. 33 Steel Pipe ........................................... 33 Urbanite ............................................ 34 Straw ............................................. 34 Dimentia and Proportia ................................... 35 Constructing the Combustion Unit .......................... 37 Mortar ............................................. 37 A Mock-up .......................................... 37 Insulation Under the Stove ............................. 39 Table of Contents

Building the Brickwork ............................. 39 Adding Insulation .................................. 40 Setting the Barrel .................................. 41 Tips on Laying Brick. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 Building the Thermal Battery ............................... 48 Materials for Building a Bench, Couch or Bed ........... 48 Lay out Exhaust ................................... 48 Connecting Stove to Bench .............................. 48 Locate Clean-outs .................................. 49 Sculpt the Thermal Battery .......................... 49 Feeding and Caring for your Dragon ......................... 50 Light my Fire .......................................... 51 Choice and Use of Paper ............................ 51 Adding Kindling ................................... 52 Stoking .......................................... 52 The Fuel You Burn ..................................... 53 Keep it Dry ....................................... 53 Kindling Selection .................................. 53 Choosing Firewood ................................ 53 Maintenance ............................................ 55 Cooking on the Rocket Stove ............................... 56 Fire! Fire! ............................................. 58 Burning Questions........................................ 59 Trouble Shooting ......................................... 64 Drawbacks of Rocket Stoves ............................... 67 Adaptations and Other Kinds of Rocket ...................... 69 The Rocket Hot Tub .................................... 70 Detroitus and the Pocket Rocket .......................... 71 The Guatemalan Cookstove: Estufa Rocky ................... 72 The Bengali Pit Stove ................................... 73 Heating Water ......................................... 74 Coffee Rocket ......................................... 75 How to Make a Pocket Rocket ............................ 76 Research Needed and Experiments .......................... 78 Case Studies ............................................. 80 Tom & Calleagh ....................................... 80 A Rocket-Fired Wood Kiln ............................... 85 Donkey’s Rocket . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86 The Reinharts ......................................... 86 Bernhard Masterson .................................... 89 Kiko Denzer........................................... 91 Flemming Abrahamsson................................. 92 Glossary ............................................. 94 More Information ........................................ 95 Resources on Pyromania ................................ 95 Books on Natural Building and Wood Burning .............. 96 About Cob Cottage Company ............................ 97 Ianto Evans ........................................... 97 Leslie Jackson.......................................... 97 Afterword............................................. 98 Thanks ............................................. 99

© Ianto Evans and Leslie Jackson Rocket Mass Heaters 7 What this Book is About This little book is about a revolutionary concept in wood burning stoves that ensures almost completely clean combustion with high efficiency use of the heat produced. Rocket Stoves are still experimental in that only a few hundred were in regular use by early 2006, but some have performed well, daily, for more than a decade. They save a lot of fuel and completely rearrange our concepts of house heating, of wood burning, and of dependency on coal, oil, hydro- or nuclear power for our comfort. Rocket Mass Stoves can be built at home by relatively unskilled people. While they are well-suited to earthen buildings with their thermally massive walls, floors and built-in furniture, they can be built into any kind of structure—from cargo containers to yurts. The term Rocket Stove has been used loosely for about twenty years to mean a fairly wide range of combustion devices used for cooking and heating. Aside from the model described in detail in this book, Rocket principles have been variously applied. Larry Jacobs and I came up with a version using only a metal drum and two stovepipes, later called the Pocket Rocket (see Detroitus: The Pocket Rocket). Later, in the late 1980’s, I helped develop a lightweight concrete single pot cook stove for urban Guatemalans. More recently, small portable cook stoves have been developed using tin cans and simple insulation. Experimental rocket-fired ovens and water heaters have also been built. Perhaps most significantly, the Rocket Mass Stoves used for house heating, which are now starting to appear all over North America and Northern Europe, have real promise in that they improve comfort and reduce the amount of fuel burned, thereby lessening the load of CO 2 on greenhouse gases. They turn almost all the wood into heat, and can store almost all of the heat generated for optimal comfort when you need it. Who this Book is For This manual is intended for pyromaniacs, tinkerers, people with curiosity about fire, owner-builders, people with an experimental mind, do-it-yourself builders who want to be less dependent on the system and have environmental concerns, and above all, those who want to be snug at home. The realm of Rocket Stoves is an experimental one whose time is overdue. Play and innovation are highly recommended. As our friend Tom Frame (see Case Studies, page 80) says, “Don’t be afraid to try something new or different. Don’t have the right part? Try something else. Can’t make a quick phone call for answers? Trust your own judgment. Just can’t figure it out? Wait, be patient. Move on to something else if you can. The answer will come. Most importantly, don’t rush this thing! You really want it to work when you’re done building it. Take the time needed.” The model of heating Rocket we describe suits the Maritime Pacific climate quite well, but it is not limited to it. Once you understand the principles of the Rocket Mass Stove, you’ll be able to modify it to your own heating needs. Rocket Stoves’ design is exploratory; their use is experimental; the attention they demand may keep you in fascination or you may find their quirks irritating. For the next edition, we will look forward to hearing (and learning from) your feedback, comments, stumbling blocks, epiphanies and wild fancies. So fire away, so to speak; send us images and drawings. If we use your material, we’ll send you two copies of the new edition. THE FINE PRINT Neither Ianto Evans, Leslie Jackson, nor Cob Cottage Company can be held in any way responsible for damage, fire or injury arising from the use of this material. These stoves are experimental and, besides, we don’t have any assets. So, enjoy to the full your fire damage and injuries. For some precautions, see Fire! Fire! (page 58).

8 Rocket Mass Heaters © Ianto Evans and Leslie Jackson The Rocket Stove in Ianto Evans’s cottage, seen from above. Dry ﬁrewood, cut thin, the small feed barrel with lid and the large heat riser barrel with tea kettle. Ianto demonstrates the stove’s use. The Combustion Unit... ...is connected to the Thermal Battery

10 Rocket Mass Heaters © Ianto Evans and Leslie Jackson Ianto Knows Why Rocket Stoves Rocket Stoves grew out of work I did between 1976 and the late 1980’s, mostly on solutions to the international firewood crisis and the problem of smoke in the homes of traditional people. In Guatemala in the 70’s, I helped worked on the Lorena stove system, which uses a sand-clay amalgam to contain the fire, hold up the pots and store surplus heat. It rapidly attracted worldwide attention and is now widely used in Latin America, Asia and Africa. Later, I worked as part of a team in over twenty countries, helping people create better cooking facilities. I spent much of a decade in villages, in people’s homes, mostly with the women who actually do the cooking. One result of my experience as a professional pyromaniac was some work in the US on the challenge of improving wood- fired heating stoves for cold climates. At that time, wood stoves had scarcely improved in more than a hundred years. The basic format had always been a simple metal box with an attached exhaust pipe. The stove heats the surrounding air, which rises to heat the ceiling, gradually circulating as it cools. To be optimally heated, you would need to be staked out on the ceiling directly over the stove. In general, the more heat lost out of the top of the chimney, the better the combustion. Clearly, this in itself is wildly inefficient. The sky has no interest in being heated. Worse, most wood stoves burn very imperfectly, that is, not all the energy available in the wood turns into heat. Much of the wood’s potential heat leaves the stove as smoke, particles, and unburned gases. The results include poisoning your downwind neighbors, excessive firewood use, and personal frustration. Clean air standards imposed by the federal government in the 1980’s attempted to limit the amount of smoke and particles put out by commercial wood stoves, but came nowhere close to ensuring clean burning. Our goal in developing Rocket type stoves was to rethink completely the question of how to burn wood inside a house in order to improve human comfort, use less firewood, and cut pollution. The results are impressive. In my own cottage I burn only about two-thirds of a cord of (fir and alder) firewood a year, while my neighbors average 3–5 cords. You can usually tell when any of the neighbors are around by the cloud of smoke coming out of their chimneys. By contrast, we burn so clean that visitors coming into my house want to know how come it’s so snug without the stove burning. Imagine their surprise when they learn that in fact, it is burning merrily. As I write, I sit by my own Rocket Stove, in my little cob house in the depth of Oregon winter. I built this stove myself in a day from recycled parts that cost less than $50. Since the late 1980’s, Rocket Mass Stoves have been my only heat source apart from the sun. For seventeen years I have daily been able to evaluate these heaters that suit me better than anything else I can find. A comparison of a year’s supply of wood. The left stack is my neighbor’s, the right is mine.

Rocket Mass Heaters

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