What is a Window Exhaust Fan and How Does It Work?

With energy costs gradually increasing, more and more people are looking to alternative cooling sources for their homes. Although not effective for the hottest of days, ventilation cooling can be one of the most energy-efficient means to beat the heat.

Window exhaust fan are relatively straightforward appliances that offer a range of benefits. Generally speaking, a window exhaust fan is simply a type of electric fan that is designed to be placed inside the frame of a window. For the most part, they are designed to fit medium to large sized windows, and expandable side barriers cover the entire window opening. There are also exhaust fans that can be installed in a ceiling, such as the Air Vent WH242MLX. Most exhaust fans have either a single, large-sized bladed fan, or even two smaller blade fans that are mounted side-by-side. In terms of speed controls, most units come with three-speed motors and can be electrically reversed in order to allow fresh air to be drawn into a home from the outside, or to exhaust warm air from inside to outside. Furthermore, there are a number of exhaust fans on the market that boast advanced features such as adjustable grills to direct airflow in a specific direction; thermostats that will turn off the fan once the temperature drops below a certain point; automatic timers; and remote controls.

However, exhaust fans can provide more than just cooling. Because they ventilate and exhaust out air, they prevent moisture buildup that can cause a range of problems such as mold growth, wood rot, paint peeling, ice dams, and even leaks. Exhaust fans can even improve your air quality, as they are capable of eliminating odors, pulling polluted indoor air out of a building, and pushing it outdoors.

Window Exhaust Fans, Attic Fans, Whole House Fans, Bathroom Fans - What's the Difference?

The above are some of the main types of exhaust fans, and although these four types of exhaust fans have different names, they all perform the same basic function - add ventilation and exhaust out air. Window exhaust fans, as mentioned above, are placed inside the frame of a window. Attic fans serve to remove trapped, hot air that tends to collect in attics and backs up into the house's living space. Whole house fans, on the other hand, suck out hot air from within a home and force into an attic, exchanging it with cooler outside air via air vents. Lastly, bathroom exhaust fans remove moisture, warm air, and odors from bathrooms.

How to Make the Most Out of Your Exhaust Fan

Heat within a home can accumulate from several different sources and make indoor temperatures higher than outdoors. This can be true in even the hottest of weather. Home lighting, appliances, and occupants generate heat as well. The first step to using ventilation as a means for cooling is to prevent as much heat from entering your home as possible, and this can often be accomplished installing attic insulation, awnings, and sun-blocking windows. Once you've prevented as much heat accumulation as possible, you can now utilize a ventilation strategy with an exhaust fan.

With that said, window exhaust fans are best used in windows that face the prevailing wind or away from it, as this prevents cross ventilation. If you find that the wind direction in your area is subject to frequent changes, you will need a reversible window exhaust fan such as the Lasko 2155A, which will allow you to either push out air of your home or pull air into it, depending on the wind direction. In some cases, you may even have to experiment with positioning the fan in different windows to see which will provide the most ventilation and the best cooling effect. If you live in a large home, you may even want to consider using an exhaust fan that blows air in through a lower level window in a cooler area and a second exhaust fan that blows air out through a hotter area.

Window Exhaust Fan Buying Tips

When choosing a window exhaust fan, look for models with more than one fan speed and pay attention to a fan's size. Although this can vary, most units range from 6 to 20 inches in diameter. An exhaust fan that is too small will have a low CFM rating and will not provide sufficient cooling and/or ventilation. On the other hand, a 20-inch exhaust fan will usually have a high enough CFM rating for two to three average-sized rooms in optimal conditions. Also, some window exhaust fans will feature Storm Guard technology which enables you to close the window with the fan mounted in the window frame.

In terms of installation, exhaust fans are also relatively easy to install, but keep in mind that location will affect your fan's performance. If possible, try installing the fan on the side of the house opposite from rooms or window in a hallway, as this will allow for air to be drawn across a room and for quieter operation.

Five Reasons Why You Should Purchase an Exhaust Fan

1. Energy Efficient: Overall, exhaust fans use little energy when compared to other cooling methods, as moving air helps remove heat.

2. Improves Air Quality: Most modern homes are built to be air tight, but this results in poor indoor air quality, as contaminants and pathogens can be trapped indoors. However, exhaust fans draw out stale air and bring in fresh air.

3. Increases Comfort Levels: Circulating fans such as window exhaust fans create a wind chill effect that makes you feel more comfortable.

4. Removes Excess Humidity: Exhaust fans eliminate excess moisture from the air, therefore preventing the formation of fungus, mold spores, and mildew. 

5. Prolongs the Lifespan of your Air Conditioner: Because exhaust fans draw out unnecessary trapped heat, this keeps your AC from overworking and even prolongs its lifespan.