Attic fans cool hot attics by drawing in outside air through attic vents and pushing hot air to the outside.
Sometimes whole-house ventilation fans that provide fresh air are confused with attic fans. They are not the same. Unlike a whole-house fan that cools the house by exhausting air from the home, usually at night, an attic fan is designed to lower the temperature of an attic by exhausting air only from the attic and replacing attic air with outdoor air, usually during the day.
One of the problems that I've run into is that some attic fans can be noisy. With attic fans it is worth it to spend a few cents more and get the better brand. Quality equipment, careful installation, and proper venting greatly decreases sound issues.
One of the secret benefits of an attic fan is that often times an attic fan is needed to preserve the warranty on your composite roofing. You didn't know that did you? Check the fine print ;)
If you have any questions about attic fans don't hesitate to call my office at 818-780-0701 I will be happy to assist you in examining the costs and benefits of installing an attic fan in your Los Angeles or San Fernando Valley home.