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How the Fan Finder sizes a space
Moving air out: exhaust and supply fans
The Fan Finder aims to change the air every 4 minutes, which is 15 air changes an hour. Floor area × ceiling height × 15 ÷ 60 gives the CFM needed, so a 10,000 sq ft building with a 20 ft ceiling needs about 50,000 CFM.
Triangle Engineering suggests a 2 to 4 minute air change to cool people, 4 to 6 minutes to cool product and 6 to 10 minutes to clear stagnant air, and notes that climate and equipment can change that.
Moving air around: large ceiling fans
A large ceiling fan's reach follows its diameter. Hunter Industrial lists 10,000 sq ft for a 20 ft ECO fan and 22,500 sq ft for its high-output 24 ft Titan, which works out to about (5 × diameter)² and (6.25 × diameter)². When a fan's own listing gives a coverage figure, the Fan Finder uses that instead.
Ceiling height
Hunter says its fans must hang at least 10 ft above the floor and at least a quarter of their diameter below the ceiling, and that 24 ft fans do best under ceilings of 20 ft and up. So the Fan Finder doesn't suggest one under a 13 ft ceiling, and it asks a specialist to confirm a large fan under a lower ceiling.
These are rules of thumb. They help narrow the choice, and they don't replace a look at the building. A fan specialist confirms every quote.
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