Visible Light Transmittance (VLT) describes the percentage of visible light (approximately 390 to 780 nanometers within the solar spectrum) transmitted through the glass. It is determined by the glass color and thickness.

What is the visible transmittance?

Visible transmittance (VT) is a fraction of the visible spectrum of sunlight (380 to 720 nanometers), weighted by the sensitivity of the human eye, that is transmitted through the glazing of a window, door, or skylight. A product with a higher VT transmits more visible light.

What is good visible transmittance?

Most of the energy-efficient replacement windows that are manufactured nowadays have a visible transmittance score of between 0.5 and 0.7—enough to let plenty of sunlight into your home, but not so much that it bleaches the fabric on your furniture and drapes and makes your home overly hot.