The study of light is subjective in some specific aspects, like color and glare, but very objective in aspects like direction and reflection. Basic optics laws tell us that when a light ray travels in a medium and finds a glass surface, for example, part of the incident ray is reflected and the rest is transmitted to the other side of the glass. Depending on glass characteristics and some other factors, the light transmitted exhibits a different range of phenomena such as heat-gain. This document provides education on design considerations to reduce the possible effects of the reflective characteristics of exterior cladding materials and glazing systems used in building construction. This document was published in October 2018.