This could be the cleanest and most sustainable way to heat a conventional home. Some people have reported that they heat their home with nothing more than the dead branches that fall off the trees in their yard. And they burn so clean, that a lot of sneaky people are using them illegally, in cities, without detection.

When somebody first told me about rocket mass heaters, none of it made sense. The fire burns sideways? No smoke? If a conventional wood stove is 75% efficient, doesn't that mean the most wood you could possibly save is something like 25%? How do you have a big hole right over the fire and not have the house fill with smoke? I was skeptical.

And then I saw one in action. The fire really does burn sideways. The exhaust is near room temperature - and very clean. The smoke doesn't come back up because a huge amount of air is getting sucked into the wood hole. Neat! I sat on one that had not had a fire in it for 24 hours - it was still hot!

how it works:

The sticks stand straight up. Only the bottom ends of the sticks burn. The fire burns sideways. Since the heat riser is insulated, it gets freaky hot. This causes a strong convective current. When the hot gasses hit the barrel, it gives off a lot of heat, which cools the gasses which get much smaller and easier to push around. The gasses that exit are usually just carbon dioxide and steam.

The real magic happens with the heat riser. The strong convective current is what makes the air get sucked in through the wood feed so that the fire burns sideways and the smoke doesn't come out. It is also the place where it gets so hot that all of the smoke is burned.

Above is a much better image showing the mighty power of the insulated heat riser, reburning the smoke and powering the whole system.

A quick video I made to explain how a rocket mass heater does what it does:

The first picture below represents the most thorough rocket mass heater design I have ever seen. Followed by the rocket mass heater that was created from that design. These are both the products of the leaders in rocket mass heater innovation, Ernie and Erica Wisner, who have built more than 700 rocket mass heaters.