Here, if it's shady, it's relatively cool, and the cooling I've thought I'd need is just the breezeway of having the aisles go all the way through, and vents in the roof. We don't have too many days of penetrating heat.
My barn has half walls in the interior, except for the tack room of course. The top half of the walls are pipe. I'm fortunate that I have no humidity here so just being in the shade is cooler, but I run fans in the summer time about a third of the time.