While using ceiling fans, type of roof affect cooling process. Apart from this ceiling fan cooling process also depend actually on the height and size of the room; the season; and the activity taking place in the room.

The basic fact of nature is that warm air rises to the top and cold air settles on the bottom. Air settles in layers from warm at the top to cold at the bottom, if left alone at equilibrium.

Here is ceiling fan direction setting recommendation in the summer and the winter:

In the winter:

Set the fan to run counterclockwise (reverse; this looks clockwise as you are looking up). This will redirect the warm air from the ceiling and down the walls and into the living space where the people actually are. In a house, you would run the fan at a low speed so that you don't actually cool the warm air that you are moving downward. If you have a high ceiling, or are trying to heat a hall or a church, you may want to increase the fan speed so that the warm air will reach the living space as long as the fan speed does not create an unwanted downdraft at the people below.

In the summer:

In a room of normal height (8 – 10 ft), you should operate your fan so that it turns clockwise (this looks counterclockwise as you are looking up), causing a more directed downdraft, especially with the fan running slightly faster. This causes a wind-chill effect because the skin evaporates slight amounts of water from the sweat glands and thereby provides cooling through the skin's surface. However, the air is only moved but not cooled! You may find that you can turn your thermostat down a degree or two and save more money on energy costs. The air blowing down won't actually cool the room though, so you should turn the fan off when there are no people (or animals) in the room.