Tuesday, May 8, 2012

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.

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