A window fan uses an electrically-powered fan blade to draw fresh cool air from the outside or ventilate stale hot air from a room. Window fan manufacturers design units to fit into open windows and sills with the addition of vertical and horizontal extenders. The result should be an airtight comfort system which keeps the air in a room circulating.
A window fan unit may only have one fan blade which can run in two different directions. One direction draws air from the outside into a room and keeps it circulating, much like a standard room fan. The other direction pulls warm air out of the room and into the outside environment. This feature may prove useful for ventilating excessive smoke or cooking odors.
Another window fan model features two independently controlled fans. These fans may work together to draw air in or ventilate air out, but quite often they work in opposite directions. The result is a more temperate room temperature, especially if a thermostat is used to control the operation of the fans. A comfortable room temperature can be set at night and the window fan's thermostat will decide to draw in cooler air, turn both fans off, or ventilate the warm room air.
Sometimes consumers will seek the same benefits from a window fan as they receive from more powerful room fans. Window fan manufacturers offer power fan options which may resemble air conditioning units or large room fans. The blade inside a power window fan unit is designed to revolve at higher speeds and provide more cooling power. A window fan can be very noisy during operation, but some manufacturers offer a 'sleep' setting which reduces noise during overnight usage.
A window fan is designed to be installed in a standard window and remain secure. Brackets included with the unit can added even more stability. Some consumers make the mistake of using a box fan inside an open window in place of a window fan. This can be a very costly error, because box fans are not designed to fit inside a window frame and can fall out unexpectedly. Besides the potential for severe damage to the fan itself, the unit may land on a passerby or valuable property. Many window fan units are also resistant to light water exposure, but should be brought inside during heavier rains and winds for protection.
