Impact resistance refers to a window design which consists of two layers of annealed or tempered glass which are bonded to an intermediate layer of a shatter proof membrane. Membranes are typically constructed of a thin plastic film polyvinyl butyral (PVB), with a thickness of between 0.015 and 0.090 inches. In the event that the outer glass breaks, the shattered pieces will stick to the PVB sheet.
Insulated windows are also referred to as double glazed windows. They consist of double glass window panes that are separated by a vacuum or gas filled space. Rather than being designed to reduce breakage impact, insulated windows are intended to reduce heat transfer. It is becoming increasingly common to offer tripe glazed windows for even more enhanced heat control.