There is no one “best” window or door. Much depends upon the performance demands, individual taste, and budget. One way to determine whether a window or door is a quality product, however, is to see if it is “certified.”
Certified products are all measured against a single performance standard, with ratings achieved for various criteria. These criteria may include structural performance, air and water infiltration resistance, thermal performance, solar heat gain resistance, and forced entry resistance. Your local or state building code may set minimum requirements for many of these criteria. Coastal communities, for example, are more frequently higher structural performance ratings to withstand strong winds.
Certified products are tested and rated to allow proper selection of a product that will meet a home or building’s needs. To be certified, products must be re-tested on a regular basis and manufacturers must submit to annual plant audits by an independent body to provide assurance that windows and doors produced in the plant are built the same way as those tested.
Participation in certification programs is voluntary. While manufacturers are not required to certify their products, state and local building codes may require windows and doors to be certified and labeled.
The two major certification organizations for window and door products in the U.S. are the American Architectural Manufacturers Association and the Window and Door Manufacturers Association. These two programs allow windows to be rated and labeled for structural performance, air and water resistance, and a variety of other attributes. Additionally, the National Fenestration Rating Council offers a program to certify energy performance. Other independent bodies offer certification services to the industry as well.
The following links can provide more information on these certifications programs, and lists of manufacturers that provide certified products.