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A powered attic ventilator, or attic fan, is a ventilation fan that regulates the heat level of a building's attic by exhausting hot air. A thermostat is used to automatically turn the fan off and on, while sometimes a manual switch is used. An attic fan can be gable mounted or roof mounted. Additional vents are required to draw in the fresh air as the hot air is exhausted. Attic fans are typically used in warmer months, when temperatures in an attic can exceed 120 °F (49 °C). A fan may be installed in an attic for the different purpose of cooling a whole house, venting hot air out via the attic; such fans are often called whole-house fans.
Mechanical attic ventilation fans may be powered in a variety of different ways. Most attic ventilators fitted to homes are powered off mains electricity. A trend towards solar-powered attic ventilators is observable in the interest of conserving electricity and lowering monthly utility bills. Wind-powered roof turbines, often colloquially referred to as "whirly-birds", are also used to ventilate attics and other confined spaces.