If you live in the North or Midwest, attic fans are worthwhile because they are cheaper to operate. They help cool the house, reducing the more expensive energy consumption of the air conditioner. In the evenings when the outside air is cool, use the attic fan instead of the air conditioning to cool the house. Your home will cool down faster, and you will save money and increase the ventilation in your attic, which should extend the life of your roof.

On the Other: Hot, Humid Climates

If you live in a hot and humid climate like the South and have air conditioning, an attic fan will pull the conditioned air out of the house, replacing it with warmer air. This is because the air is almost always warmer outside the house than inside. Also, an attic fan can pull dust and pollen into the home, causing problems for those with allergies. Attic fans will also increase humidity in the home if you live in a humid climate.

Bottom Line

Depending on the climate where you live, an attic fan can be worthwhile or not. In cooler climates, attic fans are worth considering. In hot and humid areas, attic fans are not very useful and as a result are not worthwhile.

Source:

The Natural Handyman: Keep Heat Under Control With Proper Attic Ventilation

The Natural Handyman: Whole House Fans Can Really Keep You Cool!