Tempered, laminated and insulated glass (i.g.) available. Tempered glass is a type of safety glass using heat too increase its strength compared with annealed (untreated) glass. Laminated glass is a type of safety glass that holds together when shattered. In the event of breaking, it is held in place by an interlayer of polyvinyl butyral (PVB) between its two layers of glass. Insulating glass (IG) consists of two or more glass window panes separated by a gas-filled space to reduce heat transfer across the window system.