The paper presents data showing the relationship between the sun's energy and environmental design parameters such as wind, temperature, and humidity. Each of the environmental parameters was divided into intervals and the amount of the sun's direct normal energy in each interval was calculated. Density functions of the sun's energy were calculated for wind, temperature, and humidity for each month of the year. This was done for a number of sites in the Southwest. Composite density functions were also calculated for the year and are presented and discussed in this paper.