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Window film glossary

The terms that show up on a spec sheet, in plain language — VLT, IRR, TSER, emissivity, haze, and the rest. Each links to the chapter that explains it properly.

VLT — Visible Light Transmission
The percentage of visible light that passes through the glass — how “dark” a film looks. It measures the visible band only and says nothing about infrared, UV, or heat. More →
IRR — Infrared Rejection
The percentage of infrared energy blocked across some infrared range. A real measurement, but not heat rejection: infrared is roughly half the solar spectrum, and “blocked” includes absorbed energy that partly re-radiates inward. More →
IRER — Infrared Energy Rejected
A better infrared yardstick than IRR because it weights the infrared band by the energy each wavelength actually carries — though it still leaves the visible band, ~44% of solar energy, out of the accounting. More →
TSER — Total Solar Energy Rejected
The percentage of the whole solar spectrum (UV + visible + NIR) a glazing system rejects — reflection in full, plus only the absorbed share that escapes back outside. The single most honest number on a spec sheet. More →
SHGC — Solar Heat Gain Coefficient
The admitted share of solar energy — the mirror image of TSER. The two describe the same physics from opposite sides and sum to one. Governed by NFRC standards. More →
NIR — Near-Infrared
The band of solar radiation just beyond visible light. Invisible to the eye, it carries roughly half of the sun's energy and becomes heat when absorbed. More →
Absorption
When a material takes in radiation and its atoms vibrate faster — the moment energy becomes heat. Absorbed energy doesn't vanish; some of it later re-radiates, partly inward. More →
Reflection
Solar energy turned away at a surface before it's absorbed — the only one of the “three fates” that removes energy from the system cleanly. More →
Re-radiation
Absorbed energy released again as longwave infrared. How much, and in which direction, decides whether trapped heat ends up inside or outside — and it scales with the fourth power of temperature. More →
Emissivity
How readily a surface lets go of absorbed heat as radiation. Low-emissivity surfaces hold and redirect heat differently — central to how a film's absorbed energy is finally distributed. More →
Haze
The share of transmitted light scattered out of its straight path — the optical clarity cost a film can carry. Rarely reported on spec sheets, and a real diagnostic of construction quality. More →
ASTM G173
The standardized reference spectrum for sunlight at ground level — the agreed-upon “shape” of solar energy that makes performance numbers comparable at all. More →
Plasmonics
The mechanism behind true sputtered titanium-nitride film: electrons in a thin metal-like layer selectively reflecting infrared. The reason TiN film carries its own bronze-gold color rather than dye. More →