Attic fans are an easy and efficient way to cool your home. If you live in a moderate climate, where cooling isn't necessary as frequently throughout the year, they are particularly helpful because they're much more cost-effective than a traditional air conditioning unit would be.
The reason attic fans function so well is that warm air tends to rise from a low point to a higher point, regardless of your home's arrangement. In the case of your home, the highest point in the attic. Without proper venting, this warm air collects and becomes trapped in the attic, which increases the home's overall temperature.
There are several types of attic fans you can use to vent out trapped heat and air, and each works slightly differently and have different pros and cons.
1. Exhaust Fans
Exhaust fans are the most common type of attic venting system, and they are installed directly into the attic's roof in a majority of homes. They come in sizes to fit the square footage of most homes. While exhaust fans are powered by your home's normal electric grid, they definitely don't cost as much in energy as running air conditioning full time. For peak efficiency, use exhaust fans concurrently with the air conditioning unit.
2. Solar Fans
Solar fans function similarly to exhaust fans but are even more ideal for increasing the energy efficiency of your home. As the blades of the fan spin, they draw warmer air from the attic and other areas outside and simultaneously pull cooler air in. The fan speeds the venting process and can cool a home's upper levels a full 5-10 degrees in a matter of hours.
As their name implies, solar attic fans rely on solar energy from the sun to operate. This keeps them green and efficient, but the downside is that they will only run when the sun is shining, and they are not as powerful as their electrical counterparts. Due to their reduced power, a larger or multi-level house will need more than one.
3. Static Air Vents
A static air vent isn't actually a fan, but when installed directly into your attic's roof, it encourages a cooling air exchange between warm indoor air and cooler outdoor air.
This will vent warmer air and create a low intensity draw through open doors and windows on the lower levels. Static air vents do not include any fans or spinning blade components. They will still function as needed, but without a separate fan such as the ones described below, it will be hard to notice any air movement with a static vent.
4. Whole House Fans
A whole house fan is actually just a kind of exhaust fan. Rather than installing these directly into the attic roof as you would a normal attic exhaust fan, whole-house fans are placed on the floor of an already vented attic. These are perfect for homes that have established venting systems and where cutting into the roof would either not be possible or would not fit with the architecture of the house. Whole house fans come in three varieties, all of which encourage air circulation.
Standard fans are inexpensive and easy to install, but they have no backflow prevention and will need an insulated box cover for the winter months.
Insulated Door Fans
Insulated door fans are best for areas with quick and dramatic temperature changes. The doors close automatically depending on the direction of airflow, which is directly influenced by temperature. The insulation keeps warm air from escaping in the winter months, and they are much quieter than standard fans. One drawback is that they do not move as much air as their counterparts, but depending on the size of your attic or home, an insulated door fan may be the perfect low-tech, low-maintenance solution.
Inline fans come with their own air duct system. This makes it easy to place several fans into the attic floor and lead them into separate rooms throughout the upper level. They also have louvered closures to prevent warm air from escaping. They do not move as much air, but having multiple units can compensate for this.