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Performance metrics & physics

IR Peak Wavelength

The IR peak wavelength is the specific infrared band (often 950–1000 nm) where solar energy is most intense and where window film IR rejection is typically benchmarked.

Solar IR doesn't deliver energy uniformly across 780–2500 nm. There are specific bands where atmospheric absorption is low and energy delivery is high — often around 950, 1100 and 1400 nm.

Films are sometimes benchmarked at "peak IR rejection" rather than full-band IR rejection. The peak number is usually higher (90–99%) than the band-averaged number (often 60–80%).

For honest comparisons, ask manufacturers for both peak and band-averaged IR rejection numbers. A film with 99% at peak but only 50% averaged is performing differently than one with 95% across the whole band.