Authors Erica and Ernie Wisner are the foremost builders of rocket mass heaters in North America. They have built over 700 rocket mass heater prototypes, built and compared hundreds of test models, developed educational materials and taught classes and workshops. 30-70% of our household energy budgets go to heating and cooling. Choosing how to heat your home may be the most significant decision you can make for energy conservation. Rocket mass heaters use ¼ of the wood an