Whole House Fans
A cost-efficient way to cool your house
Whole-house fans, also known as attic fans, offer a simple and inexpensive method of cooling your entire house for just pennies an hour. The fan is designed to circulate fresh air from outside the house to the inside, forcing the hot, stale indoor air up into the attic and back outside through vents in the attic roof. Whole-house fans are so efficient they can lower the temperature inside your house by five degrees in minutes.
The fan unit is mounted to the attic ceiling or the attic floor and draws air through vents that are distributed throughout your home. Before you turn on the fan, you must open a few windows or a door to keep the air moving through your house and to avoid damaging the fan or combustion-based appliances installed in your home.
Advantages
The most important benefit associated with whole-house fans is their ability to control the temperature throughout your entire home. A simple flip of a switch can cool your home in less than five minutes – an efficiency often unmatched by central air conditioners.
Whole-house fans generally cost considerably less than air conditioning systems. The cost for a whole-house fan ranges from $150 to $300, whereas the cost for central air conditioning ranges from $2,000 to $4,000. These fans also consume up to 30 percent less energy than central air conditioning or window air conditioning units.
Disadvantages
The most significant disadvantage of the whole-house fan is that, in addition to circulating outside air to the inside of the house, the whole-house fan also circulates allergens and particles that are outside of the house to the inside of the house. For people who suffer from allergies, respiratory problems, or environmental sensitivities, this system can reduce the air quality inside your home and cause health complications and discomfort. Likewise, if it is humid outside, you will increase the humidity level inside your home.
The second disadvantage is that these systems are really only effective during certain weather conditions: when outdoor temperatures are cooler than the air inside of the home, when humidity levels are low and when the levels of airborne allergens, such as pollen, are low. The most appropriate time to use a whole house fan is when the outside temperature is below 85 degrees; if it is any warmer outside or humid, it is best to use an air conditioner.
When choosing a whole-house fan you must consider the amount of noise it will produce and the size you will need to effectively cool your home. Whole-house fans, or attic fans, can potentially be very loud; ask about models that are designed to be quiet and opt for a gable or roof mounted fan to ensure the noise is as far away from your living space as possible.
To determine the size of fan you need, multiply the total square footage of your home (including the main and upper floor) by the ceiling height to calculate the amount of airflow in cubic feet per minute (CFM). To cool your home, you want to select a fan that offers between one half to one times that amount of airflow in CFM. For example, a 1,500-square-foot home with 8-foot ceilings would need a 1,500 x 8 x 0.5 = 6000 CFM fan or better. A two-speed unit that provides 8,500 CFM on the high setting and 6,200 CFM on low should work just fine.
