A Rocket Mass Stove by Juured in Estonia.

  
   
 
 
 

When a rocket stove burns it draws air in, pulling the flames down into the stove. You can see the feed here on the right but covered with two bricks. Wood is placed in relatively long lengths in the rocket stove fire box that stick out the top while they burn. The wood is gradually consumed without any smoke escaping. This rocket stove is by Juured in Estonia.

   
       

Rocket stoves have very efficient combustion, where the furnace temperature ranges from about 1000C up to 1100C. The exhaust from the rocket stove on the right winds its way within the bench to the left and turns back on its self rising just the the left of the stove to exit the log cabin. Because a Rocket Stove pushes gas along the exhaust flue, there will be pressure inside trying to squeeze gas out through any cracks.

  
       
 
 

This book by Ianto Evans and Leslie Jackson is without doubt the best guide you can find to building your own rocket mass heater.
 

During combustion there may be Carbon Monoxide and Nitrogen Monoxide present in the fumes. Both gasses are toxic so any exposed metal pipe inside the building should be thoroughly sealed to make sure no gas can escape. In the bench above the whole flue is sealed with cob (sand, clay and straw).

Wall benches like this are comfortable at about 45cm (18 inches) deep (front-to-back) and should be around 40 cm (16 inches) high. The lower the bench is the less cob (a mixture of clay, sand and straw) is available to store heat from the stove. As a seat the bench is most comfortable if it is widest at the top and undercut by about 10cm (4 inches) so there is space to tuck your feet when you are sitting and getting up.

The idea of heating a bench or bed is a very old one. In China a heated living space and bed is called a kang (PDF 700Kb) and dates back to 5,000 BC.