It's not about thermal conductivity, it's about IR transmissivity. Above a certain temperature it would reduce the IR transmitted to the inside, thus keeping th

It's not about thermal conductivity, it's about IR transmissivity. Above a certain temperature it would reduce the IR transmitted to the inside, thus keeping things cooler in the summer while still allowing the inside to be warmed by the sun during winter. Even in a desert the temperature-dependent behavior may be beneficial to cool during the night. But if it is not then yes, a different, harder coating that always reflects IR would be preferable.