The paint works by radiating in the infrared while reflecting the shorter wavelengths. On a moonless night a surface painted with this would be cooler than one

The paint works by radiating in the infrared while reflecting the shorter wavelengths. On a moonless night a surface painted with this would be cooler than one coated with normal paint, or a mirror. And really it works by radiating heat into the open sky, space. Clouds and buildings reflect a non trivial portion of the heat back compared to the open sky