Architectural glass light in industrial factories. Annealed glass is glass without internal stresses caused by heat treatment, i.e., rapid cooling, or by toughening or heat strengthening. Glass becomes annealed if it is heated above a transition point then allowed to cool slowly, without being quenched. Float glass is annealed during the process of manufacture. However, most toughened glass is made from float glass that has been specially heat-treated. Annealed glass breaks into large, jagged shards that can cause serious injury and is considered a hazard in architectural applications. Building codes in many parts of the world restrict the use of annealed glass
Heated glass system because even high e-value windows are poor insulators compared to insulated walls, and they believe heating window ejects much of the radiant heat outside. Another criticism is that this type of heating may encourage the use of larger windows in a house, making them less energy efficient. This technology has evolved since the late 1950s where it firstly evolved to be used for melting snow on glass roofs and was then effectively inverted and used as the heat source inside the building. A common commercial use of heated glass is to prevent frost from forming on the glass doors