Ventilation Natural Ventilation

Two natural forces available for moving air through the buildings wind forces and the temperature difference between the inside and the outside. Air movement may be caused by one of these forces, acting alone or by a combination of the two, depending on atmospheric conditions, building design and location.

Wind forces

When considering the use of natural forces have produced ventilation,
conditions that must be considered in the following way:
The average wind speed
Prevailing wind direction
Seasonal and daily variations in wind speed and direction
The local wind intervention buildings and other obstacles

When the wind blows, without meeting any obstacles to change the direction of movement of the air flow (and pressure) remain unchanged. If, on the other hand, the air flow occurs obstacle of any kind (such as a house or a fan), the airflow will be pushed aside, as shown in Fig. 3-1. In the case of a simple fan (see Fig. 3-2), the closed end of the forms of obstruction that changes in wind direction. Fan expands on closed and converges at the open end, thus producing a vacuum inside the head, which induces the upward flow of air through the chimney and over the head.

Temperature difference of forces

Perhaps the best example of the thermal effect of the project on the stack or chimney known as a smoke effect. Flue stack effect is produced within the building, if the outdoor temperature is below the temperature in the room. It is caused by the difference in weight of warm air column inside the building and the cooler air outside. Stream called flue effect proportional to the square root of the project head, or nearly.

Combined forces of wind and temperature

Please note that the speed, temperature and power, acting jointly, even without interference, resulting in a flow of air is equal to the sum of the two alleged quantities. However, the flow through any hole is proportional to the square root of the sum of the heads of acting on that opening. When two heads are equal in value, and vents function in such a way in order to harmonize their total air flow through the building is located about 10 percent more than that produced by either the head of the act independently under ideal conditions. This percentage decreases rapidly, as one head increase compared with others. The larger head will prevail.

Ceiling fans
Fan function is to provide storms and bad weather, the air outlet. Maximum flow by induction, the fan should be located in that part of the roof, where he will receive a full wind without interference. Ceiling fans are made of different shapes and styles (Fig. 3-3). Depending on their design and use, they can be considered as a stationary rotating the turbine, range, or syphonage.