Combustion efficiency measures how much of the energy in the wood is converted to heat. The more the better, and the less smoke. Combustion efficiency of our heater has been measured at 95%. There is nothing better than a masonry heater. The average of other wood heaters in Australia is 63%.

Heat transfer efficiency shows how rapidly the heat produced by the fire is transferred to the room. It only measures how quickly the heat is delivered, not the comfort of the room.


A combination of high combustion efficiency and moderate heat transfer efficiency is the ideal in any wood burner. The difference this makes can be seen in the graph which shows more uniform temperature with a masonry heater than with a slow combustion heater.

Masonry heater vs slow combustion.jpg


Masonry heaters are superior to other forms of wood burners in many respects, but particularly when impact on the environment is being considered. The high combustion temperature ensures maximum burning of the fuel and volatile products given off. As a result, emissions from a masonry heater are lower than any other wood burner. Research in USA shows that emissions for masonry heaters range from 0.5 – 2.0 g/kg.

This is very different to slow-combustion heaters which produce excessive smoke which pollutes the atmosphere and leaves deposits in the flue leading to reduced gas flow and the danger of chimney fires.


Wood burning for heating produces less atmospheric CO2 than using electricity or gas. The use of plantation timber and correct burning can result in a reduction in CO2 levels in the atmosphere (CSIRO. Australian Greenhouse Office). They concluded that in regard to the minimising of greenhouse gas emissions “firewood is generally more favourable for domestic heating than other sources of domestic heating such as gas and electricity". This can be seen in the following graph.


















Almost every form of energy used for home heating, even renewables, require massive investment in infrastructure, for generation and transmission, manufacture and transportation, which adds to further emissions production. A masonry heater does not require this investment and so does not consume resources or energy for this infrastructure.


There are masonry heaters in various parts of the world which have been in use for hundreds of years. Although we cannot make any such claims for our heaters, which have been in uneventful use for thirty years, they are made of incredibly durable materials; refractory concrete, brick or stone, cast iron and small amounts of steel, which, should they ever wear out, can be readily re-used or recycled.


In use, masonry heaters do not suffer the wear and tear inflicted on slow-combustion heaters by the need for constant refueling. They could well outlive some of the houses in which they are installed.

Heavenly Heat Efficiency Graph
Heat Plum Heavenly Heat

No smoke, just residual heat during a burn.

Amount of greenhouse gas from different energy sources (kg CO2 kWhr-4)