Heating and cooling benefits

Air movement can have a significant influence on human thermal comfort. Wind chill in cold conditions is considered detrimental, but air movement in neutral to warm environments is considered beneficial. This is because normally under conditions with air temperatures above about 74°F, the body needs to lose heat in order to maintain a constant internal temperature.

Unlike air conditioners, which cool rooms, fans cool people.

Ceiling fans increase air speed at the occupant level, which facilitates more efficient heat rejection, cooling the occupant, rather than the space.Elevated air speed increases the rate of convective and evaporative heat loss from the body, thus making the occupant feel cooler without changing the dry bulb temperature of the air.

Hot air is less dense than cold air, which causes hot air to naturally rise to the ceiling level through a process called convection.

In still air layers of constant temperature form, the coldest at the bottom and the warmest at the top. This is called stratification.

The most efficient and effective way of mixing the air in a stratified space is to push the hot air down to the occupant level. 

This allows for complete mixing of the air in the space while decreasing both heat loss through the building walls and roof, and building energy consumption.

To avoid causing a draft, fans need to be run slowly so that air speed at the occupant level does not exceed 40 feet per minute (12 m/min).[