Attic ventilation
Your attic is the hottest room in the house
On a 100°F Fresno afternoon an under-vented attic can pass 150°F. That heat sits directly above your insulation and radiates down into your ceilings all evening.
What an attic fan does — and does not do
An attic fan is not a whole house fan. It ventilates the attic only; it does not move air through your living space. The two solve different problems and many homes benefit from both.
By exhausting superheated attic air and drawing replacement air through soffit or gable intakes, an attic fan lowers the temperature of the surface directly above your insulation. That reduces the heat radiating into your ceilings, shortens AC run time in the evening, and slows the thermal aging of shingles and roof decking.
- Lower attic temperature, typically a 20–40°F drop when venting is balanced
- Less radiant heat gain through the ceiling in the evening
- Reduced moisture buildup in winter, which protects sheathing
- Longer life for shingles, stored belongings and any ductwork in the attic
Intake is half the system
An exhaust fan with no intake path will pull air from the easiest available source — and in a leaky house, that source is your conditioned living space through ceiling penetrations. You end up paying to air-condition your attic.
Before we install anything, we check soffit venting for paint, insulation blockage and blown-in coverage, and we confirm the intake-to-exhaust balance. Adding baffles or clearing soffits is sometimes the entire fix.
If your soffit vents are painted shut or buried under insulation, adding a fan makes things worse, not better. We will tell you that before taking the job.
Questions we get about attic fans
Attic fan or whole house fan — which first?
If your goal is a cooler house tonight and a lower bill, the whole house fan delivers more. If your attic is badly vented, fixing that first makes everything else work better.
Thermostat or humidistat control?
Both. A thermostat handles summer heat; a humidistat handles winter moisture. Most quality units offer combined control, which we set during commissioning.
Will it make my AC bill go down?
Indirectly. A cooler attic means less heat soaking through the ceiling, so the AC cycles less in the late afternoon and evening. The effect is real but smaller than a whole house fan.