Impact rated glass replacement windows are made with laminated glass. The inner layer is made of polyvinyl butyral. It is a plastic layer between two sheets of glass. Impact glass is stronger than a car windshield. The glass might shatter if a heavy object crashes into it, but it won’t break to bits. That makes wind less likely to penetrate the envelope of a home, which creates interior pressure severe enough to blow your home’s roof off.
Impact rated glass windows must meet certain guidelines in order to be marketed and sold as such. The American Society for Testing & Materials (ASTM) has strict guidelines (E1886 and E1996) for impact resistant windows before it can be certified as impact resistant. In Clearwater, for instance, the building codes state that all homes constructed after July 2001 must have hurricane shutters or impact rated glass and window frames for exterior openings in a house to protect against wind-borne debris.