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It is important to start with the understanding that most windows are made of a framing material and standard single or double strength glass. When struck with enough force, the frame or glass will break. Windows that have been tested for impact resistance are typically made of glass with an interlayer of a resilient material that will hold the glass in place when it is broken.
This glass may be treated so that when it breaks, small pieces of glass are formed which may be less likely to have sharp edges that could tear the interlayer material. These design improvements help protect the opening and the structure from potential wind and water damage. Be aware that an impact-rated product will typically withstand more severe weather conditions but may still be damaged in a storm event.
The primary purpose of impact resistant windows is to increase the likelihood that the structure and its contents will have less damage, not that the windows will survive all storms without damage.
Impact resistant windows are tested to the requirements of three standards:
These standards describe testing, which consists of ball bearings and/or a 2”x4” board used to impact the windows in specific locations and at predetermined speeds. These windows are then subjected to a cycling of pressure to simulate the winds which would be associated with a hurricane. At the end of the test, the windows must pass criteria for any tears that have formed in the interlayer.
Representative sample windows are tested to assure compliance. A window design that has passed these tests and is certified through the AAMA Gold Label Certification Program will have an “Impact Resistant” tab added to the gold label indicating it has passed this testing. This tab will have information about the type of missile, impact speed and pressure cycle used as well as the size of window tested. Windows that have not been tested to the standards previously noted will not have this tab.
A knowledgeable window salesperson or installer should be able to provide guidance regarding any state or local building codes on impact resistant requirements that might apply. To learn more about any testing your specific windows have been subjected to, it is best to contact the manufacturer directly.
Products subjected to hurricane force winds may stress the products beyond recommended design tolerances. Even though you may not see damage to the glass or frame, there could be internal or unforeseen damage that causes the future operation of the product to be reduced.
Impact-resistant glass is designed and tested to help stay connected to the window frame, to help protect a home and its contents and to help a building stay intact in a storm. This is an obvious advantage over shutters or even plywood applications, allowing the occupant to see out and allowing daylight to enter the structure during electrical power failures.