Sun radiation has three ranges: Ultra Violet Radiation / Visible Radiation and Infrared Radiation. These three types of radiation are responsible for the total energy transmitted inside the vehicle.
According to this graph:
1. It is not worth blocking the Ultra Violet radiation if the purpose is to reduce the energy transmitted inside the car. (This radiation only contributes with 2% of the total sun energy)
2. The main sources of energy are concentrated in the visible wavelength (55%) and the infrared wavelength (43%). To reduce solar transmitted energy, either we must reflect this energy, or absorb it on the glass.
3. If the glass absorbs/reflects mainly visible radiation, the passenger cell will be cooler, but it will also decrease light transmission.
4. If the glass absorbs/reflects mainly Infrared radiation, the passenger cell will be cooler, without decreasing light transmission (infrared radiation is not visible).