30d - A "rocket" stove with adobe blocks

I am convinced that rocket stoves can be of great value to institutions where there is no cooking gas and where large pots are used every day to cook a lot of food for lots of hungry mouths. These large pots can be 40cm to 60cm in diameter and 20cm to 30cm or more in height. They are heavy when full.
  

In some institutions I have seen kitchens where cooking is done on a three stone fire on the ground.

 

 

I have also seen valiant attempts at improving the situation with gas stoves only to see them abandoned (see picture above) either because the supply of gas was not reliable or because these stoves stopped working and there was no one to fix them.
 
I have also noticed that in some cases an attempt was made to install rocket stoves but these were not being used either. In one case the rocket stove was not properly built and did not work at all filling the kitchen with smoke. In another case, see picture above, these stoves were too high, unstable and difficult to use by the women and children who had to work with the large and heavy pots. 

 

 

Compared with the metal frame we see on the ground these solutions did not help at all and were abandoned for very valid reasons.
 

There are lessons to be learned from these two situations. A rocket stove must be low to the ground for easy access and stable to avoid accidents. It must also be made with easily replaceable materials because these implements do break and need to be fixed.
 

If we make use of very well tested rocket stove design principles and use the idea Dr. Larry Winiarski experimented with (see attached video), a rocket stove made out of 16 adobe blocks, we come up with the following idea:

 

 
Take 16 adobe blocks (not fired) to form a simple and insulated combustion chamber. This insulation is very important to the proper operation of a rocket stove. And a metal frame that will support the weight of the cooking pots. This metal frame is not attached to the adobe blocks.
  

The whole stove will be less than 40cm in height and looks very much like the metal frame we saw in the first pictures above. It is as if we had taken the original metal frame and inserted the adobe combustion chamber inside. We can do that if the frame is big enough.
    

The combustion chamber is built with adobe blocks stacked on top of each other as shown:

 

  

The first layer is made with 3 blocks and one half block. In the middle we place a thinner block. This central piece will improve the efficiency of the combustion chamber.
 

  

The second layer is made with another 3 blocks and one half block just like the previous one. We must leave an open gap in the front. Through this gap we will feed the firewood and air will enter the chamber. We also place a full block on the ground in front of the stack as seen in the picture. This will support the wood pieces to keep them above the bottom of the chamber.
  

 

The third layer is made with 4 full blocks. This layer will form part of the combustion chamber as shown in the picture above.
 

 

The fourth and last layer is also made with 4 full blocks. This completes the combustion chamber. The rocket stove is ready to be tested. All the adobe blocks will be left loose. No mortar is used. If one breaks we replace it. That is it. Very simple.

   

  
Use small pieces of firewood, kindling, paper and/or dried leaves to start a fire inside the combustion chamber. Just like you light any other fire. As the stove heats up, it should not take very long, the flame at the top will start turning blue or even colorless. This indicates that the firewood is burning well and all combustion gases are being burned.

These gases are released when wood burns. In a typical fire they are lost and create pollution. In a rocket stove they burn making a very hot fire.
 

It is a good idea to install the metal frame over the stack of adobe blocks before starting the fire. Later everything will be too hot to handle.
 

  

We can place the cooking pot on the stove now. The pot shown in the picture above is about 20cm in height and the stove is about 35cm high. This is a good height even for short people. There are no high heat shields and so the pots can be handled without a lot of lifting. This makes life easier for those working in the kitchen and minimizes the possibility of spills, a common cause of severe burns.
 

Heat shields are useful to concentrate the heat that otherwise gets lost all around the cooking pot. The shields devised for this stove are set on the ground. This model has two half-shields, one on one side,
  

   

and another heat shield on the other side,
  

 

making them easy to install and remove. A couple of handles would be nice too... they can get very hot.

 

In this final picture we show a larger pot. This one about 55cm in diameter and 30cm in height. Still a good height for whomever is cooking and the pot is still nicely placed to make a very good hot soup.
  

 
This type of stove does not use large pieces of firewood. It burns small pieces of firewood. This smaller firewood is cheaper and is much easier to find. Small pieces of wood do not contribute to deforestation since they can be harvested from broken branches.
    

Children of all ages do help in institutional kitchens. This is often a necessity and a good learning experience for many of them. Small pieces of firewood are easier for them to lift and handle. Less work and less accidents. This is good too. Right?
 

The attached video is by Dr. Winiarski. It is worth watching.
  

http://www.youtube.com/watch?v=XSMR2ANIZ7E
 

04a - A dwelling with good ventilation

To have good ventilation in a dwelling without fans and air conditioning units we have to create what is called the stack effect or the chimney effect.
   

 

The stack effect takes place when cooler air coming from the outside flows into a building, preferably at floor level, and warmer air, humid air, smoky air loaded with unwanted smells, leaves the building through an opening close to the ceiling.

This stack effect can be very efficient if the dwelling is built in such a way as to benefit from the wind that regularly blows in the area as represented in the picture above.
  

Let us examine some practical details of a well ventilated and insulated dwelling built to minimize the accumulation of humidity.
  
We will start with the foundations.
 

  
The foundations should be built with stone and cement or concrete blocks. These materials make them more resistant to the humidity in the ground. The foundations must be built so that the base of the walls and the floor of the dwelling are kept about 10cm to 15cm (4in to 6in) above the level of the surrounding terrain. The soil under the foundations should be well compacted and firm.
    

 

 
Fill the space inside the foundation walls with rubble, soil or a mix of soil, gravel, sand and stone and compact very well all this filling material. Do not leave in topsoil that contains organic material.
  

In this example we are building the walls with brick, adobe, mud, rammed earth or compacted earth blocks (CEB). All earth/mud based construction materials are much better insulators of heat and cold than concrete based materials. These materials need some regular maintenance and the roof overhangs need to be wide enough (40cm to 50cm or more) to protect the walls from the falling rain but it will be worth it.
  

  

 
Now that the walls have been built we can build the roof.This will be built in the habitual way. With wooden beams, joists and sticks to form a grid, the structure over which we will apply the metal sheets that will make up the roof itself. To protect the walls from the falling rain the overhangs should be 40cm to 50cm wide or more depending on local weather conditions and practices.
  

  
We could install the insulation before installing the roofing metal sheets. The insulation will go well between the roof beams. In this case we can use some matting to cover the underside of the insulation to make it visually more appealing. This insulation will protect the interior from the heat of the sun and from the cold outside.

 
After we install the roofing metal sheets (cement fiber or plastic sheets), still a good protection against the rain, our dwelling will be ready to be occupied.
   
There are some important details worth highlighting to be included while the walls are being built.

Windows and air vents
  
A good solution for the windows is to install top hinged shutters as shown in the picture. This configuration makes good protection against the sun and the rain. With these we do not have to run to close the windows when it rains.
    

   
Air vents should be as close to floor level as possible. At ground level air is always cooler.
 

  
Intake air vents can be protected from the outside with bars or strong wire mesh, and from the inside with shutters as shown in the picture above. Always close to the ground and on the windy side of the building if at all possible. If there is a shady side of the building, it is worth placing the air vents on that side because the air will be cooler there.
 

  
Exhaust air vents should be built as close to the roof as possible. In this example these vents were placed between the roof beams and protected with strong wire mesh. On the inside we can also install shutters. Exhaust air vents should be on the side of the dwelling opposite to the wind.

 

 
In this example we can see a window protected with top hinged shutters, an air intake vent protected with wood slats for better air circulation and two exhaust vents between the roof beams protected by a wire mesh.
 
Notice how the exhaust air vents are close to the roof.

When we install the insulating material we need to keep it away from the vents to ensure good air circulation.

 

From the inside it is easy to see the space left around the exhaust air vent.

  
The insulation material, using natural or manufactured materials, can be attached to the roof beams with wires, wire mesh, string or other materials.

Important points
 

We chose a simple dwelling as our example. Each one of us can modify these ideas and use additional ones. The windows may have glass panes or not. There may be bars on the windows or not. It all depends on the situation. But it is important to leave the openings required for windows and air vents when the walls are being built.
 
What is really important is:

• Foundations that are above ground level
• Earth products (mud) for the walls
• Metal sheets (or plastic sheets) for the roof
• Insulation on the inside of the roof
• Intake air vents close to floor level
• Exhaust air vents close to the roof/ceiling
• the behavior of the dwelling occupants

And a bit of imagination and creativity. 
  
Our habits
 
The behavior and living habits of the occupants is also very important. For example, during the night the air outside is cooler and we should open the intake air vents to cool off the inside of the dwelling. During daytime, when it is hot outside, we should close the intake air vents to keep the inside cool.
  
During the cooler months it may be more comfortable if we open the air vents during the day to allow the warmer air in. This air will warm up the inside of the dwelling and help get rid of humidity. At night it may be better to close the intake air vents keeping in the warmth accumulated in the walls during the day.

A well insulated and ventilated dwelling responds well to our behaviors. We change clothes according to the weather. We should also make use of shutters, air vents and insulation to accommodate to weather changes.