Engineering360: "Glass coating to keep buildings cool"

They appear to be using materials that increase the relative efficiency of a "selective surface" for rejecting all but long-wave IR energy (black box temperatures less than, say, 500°K). The suggested ability to emit to a 3°K space for cooling the building is not realistic because of the effective temperature of the sky, the presence of cloud covering, and the fairly significant percentage of surrounding surfaces at temperatures much closer to 300°K.

The material and processes are worth study and development. Practical use is probable.

JMM