Rocket mass heater
A rocket mass heater is a wood-burning, highly-efficiency heater invented by Ianto Evans that is typically made of inexpensive natural and repurposed building materials. It is designed to be used indoors and uses one-fifth or less wood when compared to a conventional wood stove to heat the same space. Heat from one fire can last multiple days, and the exhaust is nearly pure steam and carbon dioxide. Rocket mass heaters are different than rocket mass stoves.