Performance metrics & physics
Conduction
Conduction is heat transfer through direct contact between materials, contributing modestly to vehicle cabin heating when the metal body and trim become hot from solar exposure.
On a sun-baked car, conduction is what makes the steering wheel and seat hot to touch — the surface absorbed solar radiation and conducted heat to the touch surface.
Window film cuts the radiation that drives conduction. By rejecting IR before it heats interior surfaces, the conducted heat felt by occupants drops dramatically.
For Singapore drivers, the practical benefit is touching a steering wheel that isn't painful after the car has sat in sun — direct effect of cutting incoming radiation.