We’ve briefly mentioned rocket stove mass heaters before. Here’s an excellent site that compiles a lot of free info about them and has free plans. (Detailed drawings are for sale, but anyone should be able to figure out the process by looking at the illustrations, reading the text and watching the videos.)
“Rocket mass heaters in a nutshell:
– heat your home with 80% to 90% less wood
– exhaust is nearly pure steam and CO2 (a little smoke at the beginning)
– the heat from one fire can last for days
– you can build one in a day and half
– folks have built them spending less than $20
This could be the cleanest and most sustainable way to heat a conventional home. Some people have reported that they heat their home with nothing more than the dead branches that fall off the trees in their yard. And they burn so clean, that a lot of sneaky people are using them illegally, in cities, without detection.
When somebody first told me about rocket mass heaters, none of it made sense. The fire burns sideways? No smoke? If a conventional wood stove is 75% efficient, doesn’t that mean the most wood you could possibly save is something like 25%? How do you have a big hole right over the fire and not have the house fill with smoke? I was skeptical.
And then I saw one in action. The fire really does burn sideways. The exhaust is near room temperature – and very clean. The smoke doesn’t come back up because a huge amount of air is getting sucked into the wood hole. Neat! I sat on one that had not had a fire in it for 24 hours – it was still hot!”
Lots more at Rich Soil.com
Note: the self-feeding feature (vertical sticks) is important. This eliminates the most common complaint of having to frequently tend the stove.