Glass Glossary

External and internal reflectance measure how much visible light (wavelengths ranging from 380 to 780nm) is reflected off the surfaces of a material, such as glass. These measures are expressed as percentages, representing the proportion of incident light that is reflected away from the material’s surface.

It is beneficial to have low internal reflectance on the indoor surface of the glass. Low internal reflectance enhances visibility when viewing objects outdoors, particularly in overcast or nighttime conditions, as it reduces the amount of light reflected back into the observer’s eyes. This makes it easier to see through the glass without the interference of reflected light from the interior.

Conversely, high external reflectance on the exterior surface can help reduce glare from direct sunlight. However, it may also make the glass appear more reflective and less transparent, potentially impacting the building’s aesthetics and views from the outside.

Reflectance should be evaluated in conjunction with other factors like visible light transmittance, solar heat gain coefficient, and ultraviolet protection to achieve an optimal glazing solution for each specific application.