Installing new gable fan in attic gable vent. Fan has a humidistat/ thermostat combo unit attached to control fans running time. Attic fans help pull hot humid stale air out of the attic and off top floor of home out of the home so that nice cool air can move in. These fans can make anywhere up to a 10 degrees difference on top floors of homes and help to lower energy costs by making HVAC units not have to work as hard or long.