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Series 3 · Chapter 3.6

IRER: The Better Yardstick

IRER — Infrared Energy Rejection — is the documented, published answer to the last three chapters, and its definition can be quoted from manufacturer specification sheets directly.

Per the published definition on one major manufacturer's automotive documentation, IRER is the percent of solar infrared energy rejection over the wavelength range from 780 to 2,500 nanometers — and the metric accounts for the transmitted and absorbed infrared energy that will be re-radiated into a car.

Read against this series, that single definition resolves three problems at once. The range problem: 780 to 2,500 nanometers is the full band, not a 100-nanometer window. The weighting problem: the metric is defined in terms of infrared energy, not wavelength coverage. The accounting problem: absorbed energy destined to re-radiate inward is charged against the score rather than silently credited as rejection.

Infographic — IRER: The Full Band, Weighted, With the Leak Charged: One published definition resolves the range problem, the weighting problem, and the accounting problem at once.
IRER: The Full Band, Weighted, With the Leak Charged One published definition resolves the range problem, the weighting problem, and the accounting problem at once.

The published numbers show what honest accounting costs. On the same manufacturer's sheets, flagship products list IRR figures reaching 98% alongside IRER figures reaching 70% — the same films, measured by the same company, answering two different questions. The spread between a product's IRR and its IRER is itself diagnostic: it is the measured distance between the favorable question and the honest one.

Infographic — 98% and 70% — Two Questions, One Film: The distance between a product's IRR and its IRER is the measured gap between the favorable question and the honest one.
98% and 70% — Two Questions, One Film The distance between a product's IRR and its IRER is the measured gap between the favorable question and the honest one.

IRER is the strongest infrared-scoped metric in published use, and brands that publish it are voluntarily answering the harder question. One scope limitation remains — the word infrared itself — and that limitation is the next chapter.

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