Mold grows easily in South Florida. Our humid and warm atmosphere nurtures the stuff. Many buildings - like our house and a lot of buildings at FIU - provide a hospitable growing medium for mold by allowing rain water to run over their porous stucco surfaces, where it soaks into the material and promotes mold growth. This is especially acute on the north sides of buildings, out of direct sunlight.
At our current house, the decorative buttress at the front door seems like it's designed to grow thick mats of black mold. The roof sheds water directly onto the stucco, which absorbs the moisture and, since it faces north and thus doesn't dry out quickly, stays moist and hot. It's pretty gross.
We've designed tin box to avoid mold growth through three principle means. Our roofs overhang the walls of the house by at least two feet, so they should shed water well away from the walls. When the water falls to the ground, it should land on gravel, which will minimize the amount that splashes back onto the walls. And what little water hits the walls - an inevitability when the wind starts a-howlin' - will find the glass and steel surfaces either unaccommodating to mold growth, or at least easy to clean.