Monday, May 21, 2012

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.

Saturday, May 19, 2012

60 - CEBs - a social business model

The basics
The techniques and equipment required to manufacture CEBs (compressed earth blocks) is well understood. The manufacturing process has been extensively documented and tested.
One needs to obtain the right amount of the proper type of soil and have access to the equipment to build a dwelling.

A big advantage of CEBs is that they can be manufactured at the location where the building is going to be erected. Preferably not very far from where the proper soil type can be found. If one has to transport the soil or the finished blocks a long distance the advantages of CEBs start to disappear.

Now we need to find a way to put this equipment and knowledge to work.

One needs customers. Not everyone will have the knowledge and very few people will have the money to buy the equipment.

To overcome these difficulties one needs to find a business model that will be affordable by the great majority of the people who really need a better solution for their living conditions. Those are the most disadvantaged. The people I would like to serve with all the articles published in this blog.

Business model

A group of young, energetic, community oriented social entrepreneurs and investors get together and create a CEB manufacturing services enterprise.
This enterprise provides training in the form of workshops. These workshops should be aimed at the people who otherwise would build their own dwellings out of scraps wherever they could find an empty spot of land. In these workshops people would learn basic CEB construction skills.
In addition, this enterprise would:
  • buy a CINVA-type manual CEB press
  • buy a manual earth mixer
  • rent out this equipment
  • sell CEBs received as equipment rent
Step by step it would look something like this:
  • this enterprise creates and organizes workshops
  • rents out the CEB press and earth mixer
  • no up-front payment is needed
  • but an equipment security arrangement needs to be in place 
  • use of the CEB press costs 5% of the production
  • use of the earth mixer costs 5% of the production
  • the enterprise sells this production to make money  
  • invests in additional services and equipment
Example - a person has a location, gets the proper soil and rents the CEB press. This person needs to make 1000 blocks. This person makes 1050 blocks, takes the 1000 blocks needed and uses the extra 50 blocks as payment for the rent of the CEB press. An additional 50 blocks would pay for the rent of the earth mixer.

For the disadvantaged person no money is necessary but payment takes place. For those capable of paying for the rent, a price would be established based on the sale price of the excess earth blocks. 

The challenge

Some young people with good entrepreneurial minds can certainly refine this model and make it work in their community.

People living in better conditions will be more productive and will contribute to the community market place with products and services. People just need a push to get off their survival mode where they cannot contribute to the community. From this survival level people often become a burden without a chance to play a productive and dignified role in their society. 
The first building

The first building will set the stage and provide a good (or bad) example for the community. This first building could be a school, a clinic, a social center, a local shop or the actual enterprise office. Every community will have a good idea about where to start.

All that needs to happen is to start where people can see the benefit.

21 - Mixing soil for compacted earth blocks (CEB)

Compacted Earth Blocks (CEB) are some of the best construction materials we can find. They are and have been used in many parts of the world for many centuries and have proved to be worth a lot more consideration than we sometimes give them.

As the name indicates they are made out of soil that is compacted in a simple press and cured in the sun. They are not fired and are more resilient than adobe blocks. It is much easier to build with CEBs than to build with rammed earth.  

They are often manufactured in the location where the dwelling will be built. CEBs can be made with soil components only. But they can be stabilized with lime or cement to be more durable.
Since they do not consume fuel for the firing process CEBs do not contribute to climate change and deforestation. The manufacturing process uses 5 to 15 times less energy and is about 8 times less polluting than other types of blocks and bricks.

All these factors contribute to a lower production cost when compared to the available alternatives.
The CEB manufacturing process and the many construction methods using CEBs are well documented in many languages. For that reason we will only cover here some basic points on how to get the right soil mixture.
Raw materials
The basic raw material is soil with a good mix of gravel, sand, silt and clay. This type of soil can be found in many locations around us. These locations are well known in all communities and there is always someone who knows where they are.

This good soil is found under the ground layer of topsoil. Topsoil is where plants grow and will always contain a large amount of plant and animal matter. The soil in topsoil is not good for what we need. We need the more reddish soil as shown in the picture above.
Soil identification
To identify the type of soil we have we use the same identification method we used to make adobe blocks.

The above picture shows some examples of the type of results we may get. The percentages always refer to the total amount of soil in the sample. The water used and left after the test has no impact on the results.

The right soil mixture

A good soil mix for CEBs has the composition shown in the picture below. If the soil collected from the local source does no have this mix we need to add more of one of the other component until we do. It is important that our soil sample does not contain rocks or organic material such as found in the topsoil.
First we need to make sure that our soil is well ground up and has no lumps. Then we mix all the components well without water. Only then do we mix water until we get a humidity level that will allow us to make a ball in our hands. But our hands should not be wet after making the ball.
When we drop the ball from waist height the ball should break in pieces like the example in the middle of the picture above. At that point we have a good mix to make our CEBs in the press.
We may add about 5% of lime or cement to obtain a good stabilization. This makes our CEBs more resistant to breakage and more durable. Stabilized CEBs need to cure in air for about four weeks.

Thursday, May 17, 2012

22 - A manual CEB CINVA press

Manual CEB (Compressed Earth Blocks) presses exist since Raul Ramirez created the manual CINVA press in the 1950s decade.

Ever since a number of designers and enterprises around the world have published and manufactured CEB presses based on this concept. There are also a number of Internet sites with links to drawings for this type of manual CEB press.
I have been searching far and wide but I have not been able to find any plans or drawings for one of these manual presses.  In the end I decided to create my own set of plans and drawings for the manual CINVA press. The objective was to create a set of drawings with all the pieces, dimensions and details for anyone to build one.
The press I drew and filed in the Google 3D Warehouse data base was for 28cm x 14cm x 10cm CEB blocks and is intended to manufacture one block at a time. It is really intended to be a tool for the entry level builder.
I have not built a prototype yet. A few details are missing by I am confident that all dimensions are good and will be useful to anyone with access to a small metal workshop.
I will update all the published drawings and plans and will share in this blog all the missing details as soon as I have built and tested the prototype.

But if anyone is handy enough to try and build a prototype before I do, please share with us your lessons learned. We will all be thankful for that.
I am available to answer any questions and clarify any doubts.

Wednesday, May 16, 2012

10 - Modern or traditional style

Traditional or modern style? Traditional or modern materials
Two themes that have greatly influenced the way in which we have built and still build our dwellings. And the choices we have made have not always yielded the most desirable results.
Let us explore a bit these tow themes. I invite the reader to also explore these two themes with friends and family.

We know all too well the origin of the forces that made us view everything we were familiar with, everything that was traditional, as inadequate, old, and no good. We do not need to review again that part of our history.
But we know that it was due to those forces that we stopped building our dwellings the way our elders and our ancestors used to build and started imitating the style and the materials that were shown to us in the cities of concrete.
I find it very interesting that today, all over the world, we can see a revival and a recognition of that traditional style in the construction of new hotels... 
... residential buildings ...
... beach facilities ...

... and other buildings replicating and imitating our so called traditional style.
This being the case then, why can't we build our homes, no matter how humble and small, in the way that was so familiar to us, the way that was valued for so long, and is now being valued again by so many people in our countries as well as overseas?
Like this example that I find so simple, comfortable and beautiful ...
... or this one, a bit less elaborate, but with a lot of good taste ...
... and based on a mix of details and readily available materials.
I think that the times have changed and that the door is open for us to make use of so much time tested traditional knowledge. And we can enrich this knowledge with a mix of ideas to create dwellings we can build ourselves with materials readily available in nature. Dwellings that can be so much more comfortable and healthy.
Traditional building materials are very well suited to build dwellings in the so called traditional style. The style people call ecological but I call human and nature friendly.
In future articles we will identify natural building materials, traditional building materials, how to obtain them, how to build well with them and how to improve their comfort and efficiency as residential buildings.

Monday, May 14, 2012

04b - Good ventilation habits

To be comfortable a building with insulation and good ventilation still depends on the participation of its occupants.
Walls that are built with earth and clay based materials, such as cob, mud bricks or rammed earth, absorb and release heat at a much slower rate than walls built with reeds, concrete blocks or corrugated iron sheets. This is called high thermal capacity and thermal inertia.

We can and should use this ability to retain heat to control the warmth or coolness inside a dwelling. And this happens when the dwelling occupants adopt simple practices that can contribute in a big way to the comfort level within the building. 

In warm weather
We want the building to be cool during warm and hot weather. But the air will only be cooler after sunset. When the night air starts to cool off we want to open the intake air vents close to the floor and the exhaust air vents close to the ceiling/roof. This will let the cool night air in and, or at a minimum, will let air circulate due to the induced stack effect (or chimney effect).
At night this cooler air circulation will help cool off the walls and release any excess humidity that may have accumulated during the day. This cooling effect is, in reality, the release of heat accumulated in the walls during the day. And so air circulation inside the dwelling will release excess heat and humidity.

In the daytime we want to preserve this coolness accumulated during the cool hours of the night. To do this we close all air intake vents to stop the hot outside air from entering the building.
During the day the outside of the walls could be exposed to direct sunlight and absorb a lot of heat. This will not help us keep the dwelling cool during the day. During hot sunny days we should try to keep the sun away from the building walls. Wide roof overhangs, the shade of trees or other shading solutions are the best approach.
In cold weather
During cold weather we want to do exactly the opposite to what we do during hot weather. We want warm air to enter the building during the day and at night, or when it is cold, we do not want this warm air to get out of our warm dwelling.
To warm up the walls we want to open the intake air vents during the day. We also open the exhaust air vents to create good air circulation. We want to make sure that the air going into the building is as warm as possible. We want the air from the sunny side of the dwelling.

When the sun starts to go down and the temperature starts to drop we want to close the intake and the exhaust air vents to keep the warm air and the warmth accumulated in the walls to stay inside. 
An insulated and ventilated building that is built with earth based materials will maintain most of its warmth until the sun comes up again. We are still dependent on the weather, but we can take advantage of the benefits that nature provides.
These good practices are simple and will contribute the physical comfort we can obtain in an insulated building with control over its ventilation.

Saturday, May 12, 2012

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. 

Thursday, May 10, 2012

Just a thought for the week

You should not be afraid. You should think it does not take much to get something going, because there is knowledge everywhere that can help you.

Wednesday, May 9, 2012

02a - Humidity in a dwelling - how to avoid

We have already talked about some sources of humidity inside a dwelling:
  • the kitchen where water boils, the stew cooks, and water is always evaporating from pots and pans, 
  • our human bodies that constantly release water vapor, day and night, even when we are not perspiring,
  • bathrooms and toilets because hot and warm water does evaporate.
In addition we have to consider other sources of the water and humidity that enter our dwellings:
  • the roof that leaks and lets rainwater in. This water wets the interior of our dwellings and evaporates raising the humidity level,
  • the walls when poorly protected from the rain absorb humidity that will be gradually released into the inside of the building,
  • and the floor that absorbs the humidity from the surrounding soil releasing it into the dwelling.
The humidity in the soil penetrates the building floor making it wet. A wet floor will release its water contents by evaporation contributing to the discomfort of the building occupants. This is not a healthy situation since a wet floor harbors harmful microorganisms, pests, mold and various harmful insects.

For now we will concentrate on our dwelling floors. We will deal with the roof and the walls in another blog.
To control the humidity in the floor and so control the humidity levels inside our dwellings we can do a number of things:
  • build a foundation of stone or concrete blocks,
  • elevate the floor level above the level of the surrounding terrain,
  • cover the floor with some waterproof material.
A stone or concrete block foundation by itself will help but is not enough to keep the humidity and the water out. The water outside will infiltrate the soil and find its way under the foundation and into the building. Water will continue to infiltrate until its level inside the building is the same as the water level outside the building.

The solution to this situation is to raise the dwelling floor level above the outside terrain level. The humidity in the soil will still infiltrate under the building floor but will not completely infiltrate the raised floor leaving the inside of the building drier.

Even with all these precautions it is important not to build our dwellings in low lying land. Rain water will always find its way to the low lying spots in the landscape. We know this. But water that seeps into the soil will also do this. It will take longer but it will continue seeping into the building floor if the building is on low ground.
It does help to cover the building floor with a sheet of waterproof material, such as a continuous sheet of plastic, but it does not solve the problem of water infiltrations. And this solution, by itself, can prove to be expensive.
We can cover the floor of a building with a sheet of waterproof material but we should do this under the floor, as shown in the picture below. This sheet will protect the compacted soil or the paving material from the underground humidity making the inside much drier and healthier.

It is always beneficial to cover a compacted floor with some other flooring material that will make the interior of the dwelling more comfortable, healthier and cleaner, but first we need to solve the humidity infiltration problems.
If we install some flooring material without a continuous sheet of waterproof material below the floor it will always feel cold and uncomfortable in cold weather. On a cold floor we will see the formation of water condensation which will provide fertile ground for molds and other nuisances.
And we know this is not healthy for anyone.

Tuesday, May 8, 2012

05 - Protection from the heat and the cold

A dwelling needs to protect its occupants from the heat and from the cold.
Excessive heat is the cause of a common feeling of tiredness and reduces our stamina. This state of tiredness does not let children perform well in school.
Excessive heat at night does not let us sleep well and feel rested in the morning when we have to face our daily responsibilities. This lack of sleep and this feeling of tiredness robs us of our energy and our enthusiasm for many good things in life, including our sense of humor.
Excessive cold makes us wear more clothing and demands more energy from our bodies. This extra demand reduces our energy level and makes our bodies more vulnerable to the common cold, the flu and many respiratory problems.
We often say that we got a cold because of the cold weather. But it is not the cold weather that makes us get a cold or a flu. It is the extra demand on our energy levels that weakens our energy reserves making our bodies more vulnerable to these ailments common during the cold months of the year.

Excessive cold at night, just as excessive heat, does not let us sleep well.

It is very important the we feel protected from the cold and the heat when we are inside our dwellings. It is very important that a building, and especially a dwelling, provide a comfortable environment to its occupants.
We cannot do anything to control the temperature and the humidity of the outside air, but we can do a lot to control the temperature and humidity of the air inside our dwellings.

Good ventilation helps a lot, but it is also necessary to protect the interior of our dwellings from the excessive effect of the sun. This is an important role for walls and roofs and can be accomplished by insulating well walls and roofs. Insulation stops the outside heat from entering the building.
When the weather is cold, or at night when the sun goes down, good wall and roof insulation will keep the interior heat from escaping to the outside cold air.

Walls that are made with adobe, mud, mud bricks, straw or wood products offer a better insulation to the cold and the heat than walls made out of concrete blocks and corrugated iron sheets.

Mud, straw, palm leaves and various wood products are much better insulating materials for building walls.

It is very important to ensure that walls and roofs protect us from the wind and do not let through unwanted air currents. This is very important.

Dwellings that are made out of so called traditional materials are much more comfortable than those built out of concrete and iron sheets.
These dwellings can be very attractive and friendly over and above being much more comfortable.
Similarly, roofs made out of traditional materials such as straw, palm leaves or wood products offer better insulation to the heat and the cold than iron sheets, the most common material used in our dwellings and other buildings.

These traditional materials may not protect us from the rain as well as iron sheets do and may need more ongoing maintenance. Two of the reasons why they have been used less and less. The price we pay in comfort is a dwelling that is much hotter when the sun shines and much colder when the sun sets.

However we can use metal sheets protected by a layer of insulation made out of those well known traditional materials such as straw or other dry vegetable products. This layer of insulation can be applied from the inside or from the outside giving the building a more traditional look.
On the inside, in addition to straw or palm leaves, we can use bags of rice husks, or other dried shells, attached to the interior of the roof structure with a wire mesh or pieces of string or rope made of natural fibers.
As in the picture above, this may not look very nice. But we can easily improve on the appearance if we cover the ceiling with a mat made out of natural fibers as in the picture below.
There is an endless number of ideas that can be used to build a comfortable dwelling. On the oriental coast of our equatorial Africa there are buildings where the roof is separated and elevated from the ceiling of the building. Just like the picture below although the actual look is not as modern.
In those buildings a corrugated steel roof is separate from the ceiling and built over a ceiling made of wood, reeds and mud. The outside air circulates freely between the ceiling and the roof. This makes the building much more comfortable than the typical building where the roof and the ceiling are attached with no air circulation in between, or those buildings without ceiling at all.

In these buildings the ceiling protects the occupants from the cold and the heat. The roof protects the building from the direct sun light and the rain. A very practical and efficient combination.

I am going to explore this idea a bit more in another blog. I think it has a lot of potential.

04 - Natural building ventilation

To obtain natural air ventilation in a building without fans and other expensive equipment we need to create what is called the stack effect, also called the chimney effect.
The stack effect takes place when fresh air, cooler air coming form outside, enters the building, preferably close to ground level, and hot air, loaded with humidity, smoke and all sorts of domestic smells, exits the building through an opening in the ceiling
When hot air, which is lighter than cooler air, exits through an opening in the ceiling, this hot air pulls cooler air from the outside into the building.
This is a very simple and inexpensive way of creating a healthy air circulation inside a dwelling. This circulation brings substantial health benefits and physical comfort to the building occupants.

At the same air temperature, air in circulation feels cooler.
In addition we can take advantage of the wind to improve the effectiveness of this stack effect in two ways.  
One, letting the wind pull the hot, humid and stale air from inside the building as shown in the following picture.
And in the case of a dwelling with a different roof:
Another way is to allow the wind to partially enter the top of the building to create a vacuum effect which pulls the hot stale air with more effectiveness. This effect is called the Venturi effect.
This method also works well with different roof configurations: 

These are just two examples of how the stack effect can be made to work in a building. It is important to note that air must be able to come into the building close to the ground and exhaust at the top of the building.
We can now explore some practical solutions that will apply to a new building or to adapt an existing building to include this beneficial capability.
We will do that in a future blog.