rocket mass heater build and burn

Sign up for my daily-ish email, or my devious plots for world domination: I had this idea to build a rocket mass heater that was not cob. I wanted to see if a wood bench filled with sand would work well. It would have three major differences from the other rocket mass heaters that I know of. A wood-based look; much lighter, so it could be used in places with an iffy floor; and more portable: I hope it can be m