An attic fan works by drawing super-heated air out of the attic and exhausting it outdoors, while replacement air enters through soffit, ridge, or gable vents. A thermostat (and sometimes a humidistat) controls when the fan runs, typically activating once attic temperature climbs above about 100°F.
How they operate
- Thermostat senses attic temperature
- Fan activates above the setpoint (usually ~100°F)
- Hot attic air is exhausted outdoors
- Cool air enters through soffit or ridge vents
- Cycle continues until attic returns to target
Properly designed systems balance intake and exhaust so no conditioned air is pulled from below. See attic fan service for sizing and install.
