Thoughts on low cost warmth

I have been interested in rocket stoves for some time, even researching the operation and construction of simple bench-top stoves using cans and/or pipes. During one of my research forays I came across a reference to a rocket stove mass heater. With great interest I sent off for, and subsequently received, a copy of Rocket Mass Heaters, Superefficient Woodstoves You Can Build (and snuggle up to). Though the book arrived in a far less than pristine condition, it was definately worth the money spent.

Ianto Evans, pyromaniac supreme, and Leslie Jackson, the book’s illustrator and co-author, have presented the rocket stove cum mass heater for those of us who find such science fascinating. The forward says it all.

. . . revolutionary concept in wood burning stoves that ensures almost completely clean combustion with high efficiency use of the heat produced.

My interested in the rocket mass heater has as much to do with my need for the technology (and warmth) as it does my interest in the science. Even though we’re doing PAHS heating, there will be a many year lag before the the system can adequately heat our home through the winter. In the interim I need a way to keep us warm at little to no cost. Part of the “keeping warm” bit has to do with NOT having a smoking beast in my house. I don’t want the wood and its related debris, I don’t want the ash, I don’t want the smoke. I think I can manage the warmth AND all the rest with a rocket mass heater.

So here’s what I’ve learned.

The rocket mass heater can be built inexpensively and can be constructed largely out of recycled bits and pieces. For comparable square footage heating, a rocket mass heater uses less than half the wood of a conventional “efficient” wood heater. It even uses less wood than a masonry heater. In my mind that’s pretty perfect.

Combustion chamber of the rocket mass stoveThe technology of the rocket mass heater is fascinating. The magic trick the rocket stove performs is routing the heat (and smoke) back down to the level of the horizontal burn tube and out through the thermal mass. The key to getting the flow moving in the right direction is to start the draft before the fire is started. This is accomplished by lighting a crumbled sheet of newspaper in the base of the chimney (not shown in diagram).

The exhaust piping can be routed beneath the floor, which is what I’d like to do. Because our initial new living space is going to be quite small, I don’t want to dedicate any of it to the classic cob bench normally used with a rocket mass heater for holding the heat produced by this mass heater. I want to use that space for other things. And, if I route the exhaust piping through the floor, I can heat multiple rooms with a single heater.

Here’s the plan . . .

Combustion chamber and exhaust pipe locatorI want to strip our living quarters down to just the 12×24 we use for a living room which will get the addition of a small open kitchen. I want to build a 12×32 addition attached to the back of this existing building. This new addition will have a bathroom (Airstream goes away) and bedroom (construction shack becomes Terry’s TV room). The jog in the west ends of the buildings will be a glassed in sun porch. In the corner I’ll install the rocket stove which will protrude into the bathroom. The face that protrudes into the porch will be insulated. Installing the feed tube in this location will allow me to feed the stove outside our living space, keeping the smoke and debris out of our house. The sun porch will act as an airlock for our slider, which is our greatest area of heat loss.

All in all, I think this is a good plan.

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