This paper describes evaporative spray roof cooling systems, their components, performance and applications in various climates and building types. The evolution of this indirect evaporative cooling technique is discussed. Psychrometric and sol-air principles are covered and a simplified method of evaluation presented. A life cycle energy savings example is discussed. Benefits of roof life and roof top equipment efficiency and maintenance are covered as well as water consumption and performance trade-offs with alternate methods of roof heat gain control. Testimonials and case studies are presented. The gradual migration of business, industry, and populace to the southern United States was largely brought on by the advent of the practical air-conditioner, cheap electricity, and the harshness of northern winters. But while "wintering at Palm Beach" has been replaced by "Sun Belt industries" ; the compression-refrigeration cooling cycle is about the only thing separ...