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Series 1 · Chapter 1.4

The Three Bands

Solar energy at Earth's surface arrives in three bands, and the share of total energy each carries is the prerequisite for evaluating any performance claim made about glass or film. Published scientific literature places the split at approximately 3–5% ultraviolet, 42–44% visible light, and 51–55% near-infrared.

Infographic — Where the Sun's Energy Actually Lives: Three bands, three very different shares of the budget.
Where the Sun's Energy Actually Lives Three bands, three very different shares of the budget.

Ultraviolet — below 400 nanometers — is the smallest slice of the budget, but it is disproportionately destructive. UV drives the fading of fabrics and plastics, the degradation of interior materials, and skin damage. Its thermal contribution is minor; its long-term material cost is not.

Visible light — roughly 400 to 700 nanometers — is the band human eyes detect, and it carries nearly half of the total energy. This is the band most casual conversations about "heat" skip entirely, a gap the next chapter addresses directly.

Near-infrared — roughly 700 to 2,500 nanometers — is invisible to the eye but carries the majority of the solar heat felt inside a vehicle. Skin senses it as radiant warmth. Because it is the largest single band and entirely invisible, it is where performance marketing concentrates almost all of its attention.

Infographic — Invisible and Destructive. Visible and Underestimated. Invisible and Dominant.: Each band behaves differently — and each gets treated differently in marketing.
Invisible and Destructive. Visible and Underestimated. Invisible and Dominant. Each band behaves differently — and each gets treated differently in marketing.

One band is invisible and destructive. One is visible and underestimated. One is invisible and dominant. Holding all three shares in mind at once is what makes every later measurement chapter legible.

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