To cool a room down, it is generally more effective to have a fan blowing air out. This method, known as "exhaust ventilation," can help remove hot air from the room, creating a negative pressure environment that draws in cooler air from other areas. The cooler air entering the room helps to reduce the overall temperature.
The reason behind this is that when the fan is blowing air out of the room, it creates a flow of air that pulls in fresh, cooler air from windows or other openings. This process is especially effective if the outside air is cooler than the air inside the room, such as during the evening or early morning when outdoor temperatures tend to drop.
On the other hand, if you have a fan blowing air into the room, it may increase air circulation but may not be as effective in cooling down the room since it doesn't remove the warmer air. Instead, it could create a warmer, stuffier environment if the incoming air is warmer than the air already in the room.
To optimize cooling using a fan, it's recommended to place the fan near a window or an open door, facing outwards to facilitate the expulsion of hot air and draw in cooler air from outside. If possible, set up a cross-ventilation system by positioning another window or opening on the opposite side of the room to allow for a continuous flow of cooler air.
Additionally, combining the fan with other cooling methods like using shades to block direct sunlight, avoiding heat-producing appliances during the hottest parts of the day, and using ice or cold water to create a makeshift air conditioner can enhance the cooling effect in the room.