Transition Culture

10 Mar 2006

Top Five Things to Do With Oil Barrels When There’s No More Oil To Fill Them – #4. Build a Rocket Stove

This is possibly the single most wonderful things you could do with oil barrels. How about converting them into the most efficient form of space heating imaginable? All for just a few quid? In such a way as to heat the house as well as a beautiful heated cob bench, bed, whatever? I am always drawn towards technology that is simple enought that I can build it, look after it and explain it. The Rocket Stove is potentially one of the greatest inventions of recent years, and one you really should know about. Why there aren’t research facilities full of engineers running around with barrels and cob and making fires to test their amazing new creations is beyond me….

I have had the great pleasure and honour over recent years to, on a couple of occasions, work with Ianto Evans and Linda Smiley of Cob Cottage Company. They are the authors of ‘The Handsculpted House’ and have done more than anyone else to get cob back onto the radar again. They came to The Hollies twice to run cob workshops, and on both occasions it was amazing to see how they created a great group spirit and how deeply affected people were by their time with them. I also learnt a great deal from them, not just about cob, but about design and indeed about their whole philosophy. They have been a great inspiration. Besides cob building, one of Ianto’s great passions is setting things alight. A self-confessed pyromaniac, he has been designing stoves for the last 20 years, beginning with the Lorena, a wood efficient stove he designed for use in Central America. It is the Rocket Stove, however, that is his greatest breakthrough.

The beauty of a rocket stove is firstly that it creates a complete combustion, but also it allows you to send the hot air through up to 40 feet of cob mass before it leaves the building. You can therefore send it through a heated cob bench, then into a heated bed in the next room, then under the floor, and finally into your conservatory to warm your young seedlings. It means that all the heat in the wood is extracted and placed within the mass of the building. You can create sculptural features within the house which also keep you warm. This is pretty close to genius as far as I’m concerned.

Last summer they built one at The Hollies as part of a 10 day cob building course. In the picture on the left you can see the first stage of it, just built like that with fire bricks. Ianto made this, and then made a fire in the lower end. You would expect to see the whole place fill with smoke, but all that comes out of the end is warm air with a slight scent of wood. No smoke. Just warm moist air. It was amazing, and something to do with the design creating a complete combustion. The lower end is called the ‘feed tube’ and you put wood in on its end so that it self feeds into the fire. It then goes through the horizontal part and then up the ‘heat riser’.

This is super insulated, allowing the wood to completely vaporize and burn at temperatures up to 1100F, so that only steam and carbon dioxide exit through the flue. A barrel is then placed over the heat riser (see right), which then sends the heat down again and into a pipe that takes it wherever you want it to go (see below left). The barrel can be designed to be partially cobbed in, and you can cook on the top if you want to. It is wonderful. If you design your house properly you can get the heat into different rooms. Because it has a complete combustion it is highly efficient, and so you can spend more time doing the things you like to do and less time splitting wood.

Even in a hemp or a strawbale house, the core of the house could be cob, with the flue running through it. The best place to find out more about rocket stoves is by reading Ianto’s book on the subject, called Rocket Stoves to Heat Cob Buildings; how to build a super efficient wood fired heater, or by doing a course with Ianto (visit the Cob Cottage Company website for more information.