I think the most promising method in humid areas would be geothermal cooling. For instance, in Phoenix Arizona right now it is about 40C. However, about 15 feet underground it is about 26C. In Shreveport Louisiana it is about 34C at 45% humidity, but the ground temperature is 19C.<p>Geothermal cooling and basements just make so much sense for keeping cool in killing temperatures when electricity isn't available.