Types of Ventilation

A. Natural Ventilation:

• Air exchange from the windows, doors and other openings is called natural ventilation.
• It is acceptable and preferable due to cheapness.
• Natural ventilation of the building is generated by two sources:

a. Thermal force: warm air or stall air becomes lighter than fresh air as fresh air enters to the building. Warm stall air moves up and exists through openings.

b. Pressure difference: A farm house itself is barrier for wind blow. Windward face of the building accumulates air or pile of the air developing the high pressure zone. Whereas leeward face of the building creates the low pressure zone/ suction zone.

Pressure difference = windward pressure – leeward pressure, which causes the circulation of air.

B. Artificial ventilation:

• It is also called as forced ventilation. It means that the air exchange rate in ventilated room is established by fan. It differs from natural ventilation in being less dependent in wind velocity, pressure difference and continued energy consumption.
• Ventilation system includes two main parts : Inlet and Outlet.
• One of them are adjusted with fan or if required it may be adjusted in both inlet and outlet so that it creates equal pressure system.
• In the farm house the total length of opening should be 50%, 42%, 33% in 1 storey, 2 storey, 3 storey building respectively for better ventilation.