The exterior environment of a building envelope is subject to ever-changing environmental conditions such as wind, humidity, rain, sun and ambient temperature. One of the most significant influences on the building envelope design is the sun. The sun is composed of ultraviolet, visible and infrared light that is dynamic and constantly changing relative to the building. Designs that do not take the sun's influence into account can subject the occupants of the building to conditions such as uncomfortable glare, solar heat gain, variable temperatures, and the early decay of fabrics, and surfaces that fade over time. This document discusses the characteristics of dynamic glazing which can mitigate against the influence of the sun. This document was first published in September 2011, and updated in 2018.