Impact-resistant windows consist of a tough plastic or polyvinylbutyral interlayer sandwiched between two pieces of glass, which provides extraordinary strength against hurricane force winds.
The interlayer is engineered to reduce the likelihood of an impact fracture in a high-wind storm. A flying projectile could shatter the outer pane, but the interlayer would keep the window intact.
According to the Miami-Dade County Building Code Compliance Office, impact-resistant windows and frames properly installed do not require shutters. New homes with regular glass are required to have shutters.