Whole House Fan Cost Estimator
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How it works
A whole house fan pulls cool evening air through open windows and exhausts hot air into the attic — cooling the house and the attic structure for pennies an hour. In the right climate it cuts AC use 50–90% across the cooling season.
Sizing is by CFM vs floor area: roughly 3 CFM per square foot of living space (adjusted for ceiling height). A 2,000 sq ft home with 9-ft ceilings needs about 6,500–7,000 CFM. Undersized fans just make noise.
The catch is climate: it works where evenings cool down (most of the US except the humid Southeast and desert Southwest summers). And get the insulated damper model — a standard louvered fan is a giant heat leak all winter.
Frequently asked questions
How much does a whole house fan cost?
$1,500–3,500 installed: $800–2,200 for the unit plus ~$900 pro install. Quiet ducted systems run $2,500–4,500.
How does it differ from an attic fan?
A whole house fan cools living spaces by pulling air through windows; an attic fan only ventilates the attic. Different jobs — the whole house fan is the comfort upgrade.
Will it replace my AC?
In mild climates with cool evenings, largely yes. In hot-humid climates, it extends comfort and cuts AC runtime but will not replace it. It shines in shoulder seasons everywhere.
What size do I need?
About 3 CFM per square foot of living space (adjusted up for tall ceilings). This calculator sizes from your square footage and ceiling height — most homes land at 4,000–8,000 CFM.
Do I need more attic ventilation?
Yes — roughly 1 sq ft of net free vent area per 750 CFM, or the fan pressurizes the attic and underperforms. Many installs need added soffit or gable vents.
Are they noisy?
Standard models: noticeable (like a strong bathroom fan). Quiet/ducted models: whisper-level. If bedrooms are near the fan, pay for the quiet version.
What about winter heat loss?
A standard louvered fan leaks heat all winter. Insulated-damper models seal shut (R-5+) — worth the $600 premium in cold climates. Or build an insulated cover box.
Can I run it with windows closed?
No — it needs open windows for intake air (2–3 windows, 3–4 ft open each). Running with everything closed starves the fan and can backdraft fireplaces and water heaters.
How much does it cost to run?
$0.10–0.30/hour — a tenth of central AC. Running 6 hours on summer evenings costs under $50/month while offsetting hundreds in AC.
Is DIY installation feasible?
Yes for handy homeowners: cut the ceiling opening, mount, wire to a switch/timer. The critical parts are proper sizing, sealing, and adequate attic venting — get those right.