Using Super Efficient Rocket Mass Heaters To Warm Your House

The History Of Rocket Mass Heaters

The true history of the rocket mass heater reaches back to Russian and Scandinavian masonry heaters. To understand how these heaters got started, you need to go back to around 1550. Europe was under something called the “little ice age”. The amount of wood available was replenishing and the amount needed to heat homes was literally burning down forest. Over the next 100 years the stoves to come out of that were called masonry heaters. These heaters are really efficient and could even burn non-wood materials. It wasn’t uncommon for animal dung to be used. I believe this is where Dr. Larry Winiarsky from the Aprovecho Research Center got his idea to created the modern rocket mass heater. His concept was created in 1982.

Efficiency Of Rocket Mass Heaters

When living off grid, conserving your resources is really important. If you live in the forest, you’ll likely have a plentiful supply of wood, but you will still have to cut it down, chop it up and haul it to your wood pile. On the other hand, you might have to buy your wood because you live in a place that doesn’t have a lot of trees. Either way, being able to use the least amount of wood possible to heat your house is what a rocket mass heater is all about. These systems will use as little as 10% of the wood a normal wood stove would use. One way a rocket mass heater conserves the firewood is by storing heat in a mass. That mass is typically cob bench/couch that people can sit or sleep on. After burning your fire for two or three hours, the mass will be able to store enough heat to last all day. In some cases, the mass will store heat for up to 30+ hours. By reducing your need for wood, you’ll save money. In addition, you also get to spend less time hauling wood, stacking wood, and retrieving it. In almost every way, rocket mass heaters are super efficient.

Safety Of Rocket Mass Heaters

Most wood stoves have two main safety concerns. The first is the direct heat from the metal burn box. Regardless of what type of wood stove you’re using, you will burn yourself if you touch this. The second major safety issue is creosote. Non-insulated flues will build up creosote and eventually, if not cleaned, it will catch fire. Many people have lost their home due to creosote fires.

The advantage you have with a rocket mass heater is the burn box recycles the smoke that contain the creosote and burns it in the box. By the time the smoke moves through the burn box and moves into the flue, it mostly only has CO2 and possibly some moisture. There is no chance of a house fire being started due to creosote. This makes rocket mass heaters safer than any other method of burning wood.

Rocket Mass Heaters And Rocket Stoves

Rocket stoves operate similar to the burn box of a rocket mass heater. The difference is they smoke isn’t recycled through a burn chamber and the fire is used to directly cook food. If you take a rocket stove, add a burn chamber to recycle and burn the volatile organic compounds in the smoke, and then pass the heat and smoke through long tubs buried in a cob bench, you’d have a rocket mass heater. Whether it’s a rocket stove or wood stove, once the wood has burned up, the stove quickly cools down and the room stops receiving heat. The advantage of a rocket mass heaters is the mass that absorbs and slowly releases the heat over a long period of time. This is similar to the science described in our article on thermal mass.

Do Rocket Stoves Smoke?

Yes and no… to get started, the stove can smoke a little. This can be mitigated by placing a small fire deeper in the burn box or flue to draw the smoke through the system correctly. Once the fire gets started and is burning properly, there is almost no visible smoke release. You can stand outside and stare at the flue and you won’t see smoke. The systems are super efficient and burn almost everything within the fire box and fire chamber.

Rocket Mass Heater Wall

I haven’t seen anyone else do this, but I want to build a rocket mass heater directly into a wall instead of a bench. I wouldn’t do this with an external wall because you’re going to lose heat to the outside and waste your wood. By using an internal wall, all the heat will be trapped and stored inside the house. Over an evening this will slowly release the heat and warm the rooms on either side of the wall. Imagine using this to heat a wall between two bedrooms. The burn box can heat one room. For example the living room, keeping it warm while everyone is up and spending time in it. Then when everyone goes to bed, the wall would be able to kept two bedrooms warm throughout the night.

Renewable Fuel For Rocket Mass Heaters

Within our article on Earthships, we discuss using water four times. The last use is to create a leach field to water plants. I cool idea is to use this field, which very few people would want to eat the plants from, to grow plants that can then be used as fuel for the rocket stove. The waste water is a great fertilizer and growing your fuel is an awesome way to take things full circle.

Depending on which agricultural zone you live in, you could start growing fast growing trees such as poplar or weeping willow. These trees grow several feet each year. If you calculate how much wood you’ll need each year, you can plant that volume of trees each year. For the first six years, you will add to the “forest” you are creating. One the fifth year you will chop down the trees from the first year and replant them. That batch of wood will need to cure for a year. From that point on, each year you chop down the oldest trees, and replant a new crop. At the six year mark, you will have a lifetime supply of firewood that replenishes itself every year. There are other options. Fast growing vines, shrubs, and bushes could also be used. Newspaper, cardboard, and paper waste can all be used. Because the chamber in the rocket mass stove is burning so efficiently, there is little worry about creosote or other waste. Occasionally you may need to vacuum out the ash. In most cases there is very little ash to worry about. The ash that is present can be spread in your garden or used to make stuff like soap.

Summary Of Rocket Mass Heaters

Rocket Mass Heaters are an excellent tool to keep you off grid and energy independent. Due to their super efficient use of wood, you will reduce your need to buy or harvest more wood. In almost all documentation I can find on the efficiency of rocket mass heaters, they are 8 to 10 times more efficient than any other method of burning wood. By building your home with a design that reduces your need for heating, you are compounding the benefits. Part of a life lived free is reducing your dependency on others to help you survive while making life as easy as possible for you.