Whole House Fan Size Calculator
Estimate whole-house fan airflow from building volume and target air changes, then compare installed fan capacity and operating cost.
Default project preview
4,800 CFM
Required per fan
4,800 CFM
Installed capacity
5,000 CFM
Capacity margin
+200 CFM
One air change
2.88 min
Calculator
Build the material order
Your order will appear here
Enter the project details and calculate a rounded material estimate.
Methodology
Transparent calculation
BuildMeter converts every input to a consistent internal unit, applies the selected allowance, and rounds products up to whole purchasable units.
Building volume = floor area × average ceiling height. Required airflow = volume × target ACH ÷ 60 for CFM, or volume × ACH for m³/h.
FAQ
Whole House Fan Size Calculator questions
Why does a whole-house fan need attic exhaust area?+
Supply air entering the attic must have a safe path outdoors to prevent excessive pressure.
Can the fan run with closed windows?+
Operating instructions usually require suitable open inlets; follow the manufacturer and installer guidance.
Does this replace HVAC cooling?+
No. It exchanges indoor air with outdoor air and works only when outdoor conditions are suitable.