The best hurricane windows will be constructed from several layers of glass and plastic, similar to an automobile windshield. Typically, the two outer layers are made from high-impact glass and the inner layers are plastic film. This construction ensure that if the glass shatters under impact, the inner film holds the shards in place and also serves as a barrier to wind and rain.
A reputable window dealer or manufacturer will certify its products against hurricane-related impacts. Testing should conform to a standardized, approved method, such as the Miami-Dade County hurricane impact test or the ASTM E 1996 Standard Specification. The windows should be clearly labeled as to which of the standards they were held to, along with the maximum wind speed rating.
The effectiveness of hurricane windows can be severely compromised by improper installation. The best way to avoid this is to choose an installer with a proven track record of quality installations. Ask your friends and neighbors for recommendations and ask the dealer for references. Also, check with the Better Business Bureau to make sure no complaints have been filed.