How high up should a barn loft be?

I'm designing my dream barn and I want to be accurate. My barn will have a loft for hay, feed, and tack storage and teaching ground lessons in the barn (like on colors or the parts of a saddle) and convening in general. Obviously, it will be supported by reinforced steel beams. But I am getting ahead of myself here! If I plan to hang ceiling fans from the beams over the stalls, how high up should my loft be?