Its not in the code, unless we consider that the code requires us to install equipment acording to manufactures requirements. Most fans for residential use (Hunter, Hampton Bay, Emerson, Concord, ) to name a few, stipulate a minimum of 7'- 0" from the blade to the finish floor. I do not have a code book handy, but will try to get the specific code for this tommorow.
There is no code requirement regarding ceiling fans. Many homes have 7ft6in ceiling heights so it's impossible to mount a ceiling fan higher than that. Consider that most units hang approx 9in from the ceiling to the bottom of the blade meaning the blades are 81" from the floor.
My old (1996) copy of the BOCA code states (words to the effect of) no part of the ceiling, including fixtures attached thereto, shall be less than 7 feet from the floor. If you have a newer copy check section 1200-1207.
