AAMA 101 provides guidance for rating windows and doors, which are described as performance grades (PG) and are based on the design wind pressure determined from the basic wind speed adjusted for height and exposure. Buildings in hurricane prone areas are commonly required to resist pressures induced by wind blowing more than 120 miles per hour, which translates to 40 or more pounds per square feet (PSF) or a PG40 rated window or greater.

Windows tested in accordance with AAMA 101 are required to pass a water penetration test using simulated rain and air pressure differential at 15 percent of the PG. Architectural type windows require 20 percent. Additionally, windows tested in accordance with AAMA 101 are required to pass a structural test with simulated air pressure at 150 percent of the PG. This means there shall be no permanent damage to glass, framing, fasteners, hardware, or other components of the window.

Major hurricanes are defined by the National Hurricane Center and National Oceanic and Atmospheric Administration to be a category 3 or higher on the Saffir-Simpson Hurricane Wind Scale. Sustained winds need to reach 74 miles per hour to be categorized as a hurricane, and 111 miles per hour to be considered a category 3 major hurricane.

During a hurricane, windows are often exposed to winds that approach (or exceed) their design pressures, but it is critical to know that most windows are designed to withstand 150 percent of their ratings before experiencing any structural or physical damage to their components.  Alternatively, windows are only designed to resist water penetration at 15 percent of their ratings which is commonly exceeded during hurricane categorized storms. If a window leaks during a hurricane, that doesn’t inherently also mean the system has structural damage or has been compromised by the storm. Windows can leak through joints within their system from wind-driven rainfall and not have components permanently damaged or compromise the window.

The progression of damage helps to determine the extent of damage (if any) a window has experienced from hurricane winds. Moisture ingress through windows often occurs first, followed by impact damage from windborne debris, then structural damage begins to occur from direct forces from the wind. It is commonly misunderstood that if windows leak, they are also compromised. In reality, windows can leak without compromising their ongoing performance values or have a permanent impact on the system.