Rocket Mass Heater Guide: An Energy-Efficient Heating Option

In the winter of 2017, the Energy Information Administration (EIA) estimated that it would cost an average of $644 to heat a home with natural gas, $980 with electricity, $1,462 with heating oil, and $1,661 with propane. For many households, this is one of the significant utility expenses. For many, it is also a substantial contributor to greenhouse gas emissions. If you heat with natural gas, you can expect to emit an average of around 6,400 pounds of carbon dioxide each year. In comparison, electric heating systems contribute an average of 4,700 pounds. 

New technologies such as a programmable thermostat or this solar heat pump have the opportunity to drastically reduce or even eliminate greenhouse gas emissions associated with heating your home during the winter. Homes are continuing to increase in size, which subsequently increases the heating demand. One study finds that homes built between 1990 and 2001 used an average of 43,000 Btu per square foot of heated area per year. As homes get bigger, more energy will be needed to stay warm during the winter.

The Growth of Wood as a Heating Option

Your grandparents might have heated their home with a wood stove. The image of splitting wood during a snowstorm to warm the house is most often considered nostalgia. 

However, the 2010 Census found that wood was the fastest growing heating fuel in the United States. In 2010, around 2.4 million households used wood as a primary heat source, while up to 12 percent of all households used wood for secondary heating purposes. 

The main benefit of using wood to heat your home is trees are a renewable resource. The oil or natural gas your burn to heat your home will never again be available. Trees like the Douglas Fir or Cedar are fast-growing and grow to a harvestable size within 40-50 years. 

As a fuel source, trees will actively capture and sequester carbon dioxide from the atmosphere while they grow. Burning wood creates greenhouse gas emissions to the tune of 200 g of CO2 per kilogram of wood burnt. However, trees can absorb up to 1 ton of carbon dioxide by reaching 40 years of age. This absorption makes them carbon neutral or even a carbon positive fuel source for heating your home.

How to Build a Rocket Mass Heater for Under $100

While we don't recommend you do this, below is a simple example of how easy it can be to improvise a rocket mass heater for a low cost. Instead, we recommend opting for rocket mass heaters that have undergone safety certifications and are sold by some manufacturers in the following section.

Rocket mass heaters can offer you a sustainable way to limit the CO2 emissions associated with heating your home. What's more impressive is with a bit of innovation and creativity, you can build one yourself for under $100 while simultaneously incorporating a heated bench into an area of your home. 

• Firstly, you will need to build a J-shaped combustion chamber from fire bricks available at any fireplace supply store. The wood you burn is fed vertically into the opening of this chamber. On top of this J-shaped combustion chamber, there is a 55-gallon metal drum or barrel. This drum or barrel will capture the heat that passes through the vertical rise of the combustion chamber and radiate the heat out into your home. You can choose to leave the metal barrel exposed for maximum radiant heat. You can also surround it with brick, stone, or some other dense material. It will act as a thermal mass to capture, store, and eventually release the heat into your home. 
• Horizontal metal ducting acts as the "chimney" that carries the exhaust out of your home. Unlike regular chimneys, this metal ducting is horizontal (instead of vertical). Its outer layer is some form of thermal mass such as brick or cob (an earthen material) usually made into a bench. This "thermal bench" thus further captures the heat from the exhaust and radiates it back into your home. By the time the exhaust vent eventually leaves your house, it is usually nothing more than water vapor and CO2 with minimum smoke.

Who Builds Rocket Mass Heaters?

If the thought of building a rocket mass heater is intimidating, there are companies on the market tested to specific safety certifications and might fit with local building codes.

Liberator Rocket Heaters

Liberator Rocket Heaters are tested to the Underwriters Laboratories-1482 safety standard. They can consume a range of fuel types, including pellets, sticks, twigs, split cordwood, and other pieces of wood that are less than two inches in diameter. A simple rocket heater without accessories costs $1,250. However, you should be able to notice savings within a couple of years due to a drastically lower (or even non-existent) heating bill.

Rocket Heater Gamera

Rocket Heater Gamera offers high-quality rocket mass heaters that can incorporate a horizontal exhaust system of up to five meters. Their most simple stove costs 925 euros, plus shipping costs.

As winter begins to approach, adding a rocket mass heater as your primary (or secondary) heating source is a great way to cut back on your heating bill. It also reduces the greenhouse gas emissions associated with heating your home.

Article by:

Tobias Roberts

Tobias runs an agroecology farm and a natural building collective in the mountains of El Salvador. He specializes in earthen construction methods and uses permaculture design methods to integrate structures into the sustainability of the landscape.