I can actually talk a fair amount about the architectural design of Antebellum houses, which did an extremely good job of mitigating the heat and humidity. Extremely high ceilings with an open floor plan that allowed heat to rise to the attic, with high windows that allowed the breeze to bring in fresh air. In addition, deep porches shaded the walls, shielding the building from the sun. The central entrance of an Antebellum mansion would open up to a large open atrium, usually stretching ~3 stories. This would let air flow from one room to another, further cooling the place. The whitewash typical of Gone With The Wind style houses also reflected heat.