Rocket Stove Mass Heater. "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"
All About Rocket Mass Heaters! These are super-efficient wood burning heaters that you can make using common materials. They use far less wood than any woodstove out there. Shown, rocket mass heater super duper vortex of smoke reburn combustion awesomeness!