What's the best way to prove a product will perform as promised? Independent testing. It's why the Vinyl Siding Institute (VSI) established the VSI Vinyl Siding Product Certification Program.

Administered by Architectural Testing, Inc. of York, PA, the program allows manufacturers to certify with independent, third-party verification that their products meet or exceed the testing requirements specified in the industry standard for quality – ASTM D3679. In addition, manufacturers can certify their product colors meet the ASTM D6864 standard for color retention, so you can be sure the vinyl siding you select will resist major color changes in a variety of climates.

There are more than 1,000 products on VSI's official list of Certified Products and Colors. In 2004, more than 34.6 million squares of vinyl siding were manufactured in the United States. (A square equals 100 square feet of siding, or enough to cover a 10-foot x 10-foot area.) More than 96 percent of those squares (by companies reporting) were certified through the VSI Vinyl Siding Product Certification Program.

Another key test of quality is how long manufacturers are willing to warrant their products. Warranties offered by vinyl manufacturers typically last a lifetime and can be transferred to the next owner.