Efficiency is a big deal in everything we do. Heating a home with oil or a fireplace is not terribly efficient though. Definitely not efficient enough for living off the grid on our homestead. So what should we do instead? Build a rocket mass heater of course!
What is a rocket mass heater? A rocket mass heater is a wood burning heater that burns sideways sending smoke into a heat riser which then sends the smoke out into a bench and finally the exhaust lets out around 90 degrees. I know that it sounds a little funny, but check out the picture below and I’ll try to explain it better.
The wood to burn goes into a small opening and is gravity fed into the burn chamber. The “rocket” part of the stove is the super insulated heat riser. The insulation causes it to burn hotter and more fully. The super efficient burn is what causes the fire to suck in sideways towards the heat riser. This does mean that you have to get the fire going before it is efficient. All that means is that you will get some smoke back while you are starting the fire. All this heat is then pushed out into a tube which is located inside a large thermal mass. Often the thermal mass is a cob bench. The thermal mass absorbs the heat, stores it, and slowly releases it into your home. The benches only reach about 100 degrees so they are perfect for sitting on to warm yourself up, not burn you. Once the heat running through the thermal mass finally reaches the exhaust point, it has cooled off to just above room temperature.
The reason this whole set up is so efficient is for a few reasons. You get a complete burn. There is no wood wasted in ashes or creosote. That also means less need to clean the system. The burn is hotter than a standard wood stove so you are getting more heat from the system. The heat is then absorbed into the system so all the heat that would normally just escape through the chimney is being stored for use in your home. The actual exhaust is already mostly cooled off. Basically, there is nothing wasted.
This is the most efficient heating I have found so far. I plan on building a home with passive solar heating, but I will likely need something extra and this should do the trick. So now to build a rocket mass stove to see how well that works for me. A simpler practice project for us to start on.
Here are some links for more info: