Performance metrics & physics
Radiant Heat
Radiant heat is energy transferred by electromagnetic radiation rather than direct contact or air movement; the dominant form of heat reaching a vehicle interior is solar radiant heat through glass.
Heat transfers by three mechanisms: conduction (contact), convection (fluid movement), and radiation (electromagnetic). In a parked car under sun, radiation dominates — the metal body conducts some heat in, ambient air moves around it (convection), but the sun radiates through the glass directly into the cabin.
Window films target the radiation mechanism specifically. They reflect or absorb the radiant energy before it enters the cabin, dramatically reducing the heat load.
Once heat is inside the cabin, all three mechanisms contribute to occupant discomfort. The smart intervention is at the entry point — the window.