Whole House Fans – An Air Conditioning Alternative

By Mark J. Donovan

Whole house fans are an excellent alternative to air condition for cooling your home, as they typically require only 25% of the power of an equivalent air conditioning system. In addition, whole house fans are lower cost and easier to install then central air conditioning systems. However, whole house fans are more suited for areas where summer day temperatures do not regularly exceed 80o degrees fahrenheit.

Whole house fans are ideal for small homes, or homes that do not have air ducts already installed in them. For example a small home heated off of forced hot water would be a great candidate for a whole house fan system.

Whole house fans are large fans that usually reside in the attic, and are positioned over a main hallway.

A whole house fan operates by drawing in large volumes of cool air from the outside, via the home’s windows, and pulling the hot air from the living space out via attic vents.

Due to their size, and the high speed that homeowners typically run them at, whole house fans have been known to be notoriously loud.

Whole house fan technology has improved over the years thus eliminating much of the noise associated with older models. All metal, welded frames fans work best as they have fewer parts to rub together and create noise. Also if properly installed, motor vibration noise can be prevented by installing the whole house fan on rubber mountings.

In addition, there are many things a homeowner can do to reduce or prevent the fan noise. First, it is usually best to install the largest whole house fan possible. A smaller fan has to turn much faster to draw the same amount of air as a large one - the higher the revolutions per minute (RPMs) the louder the fan noise. In addition, smaller fans with higher RPMs typically have higher failure rates. Second, the higher number of fan blades the quieter the fan. So when looking for a whole house fan it is best to select the largest model possible with the highest number of fan blades.

Sufficient attic venting is required when installing a whole house fan. Typically 1 square foot of net free venting is required for every 700-800 cubic feet per minute (CPM) of air flow. Frequently, there is insufficient attic venting for whole house attic fans, so it is critical that additional attic venting be installed when installing a whole house fan. Inadequate attic venting can also cause noise and reduce the efficiency of the whole house fan.

Typically homeowners have whole house fans on timers that turn the fan on-and-off in the early evening. This also helps to mitigate the impact of any noise associated with the fans. Whole house fans are not usually installed with thermostats, as whole house fans require some homeowner prep. Windows must be opened prior to the fan turning on for cooling to actually occur and to prevent the possibility of pilot lights from going out.

It is recommended that a whole house fan be installed by professionals as they can ensure that the appropriate sized fan is installed properly and that adequate attic ventilation can be created.
Typically a whole house fan can be installed with 1-2 days.