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Performance metrics & physics

Mid-Infrared (MIR)

Mid-infrared (MIR) is the infrared band roughly 2500–25000 nm, primarily emitted by warm surfaces rather than the sun directly, and matters for building thermal performance more than for window film.

MIR is the band of thermal radiation from warm surfaces — a sun-heated dashboard re-radiates in the mid-infrared. Window glass and films typically don't transmit MIR strongly anyway, so it traps heat inside.

For automotive applications, the dominant solar input is NIR, not MIR. Films focus on NIR rejection.

For architectural applications, MIR matters more — low-e architectural film is engineered to reflect MIR back into a room, reducing heat loss in cold climates.