Fenestration is defined as "any opening in a building...including skylights." This term is often used in ratings, reports and certifications of skylights. Several organizations offer evaluation services via testing by independent labs. Manufacturers then use these results to promote their skylights.
The National Fenestration Rating Council (NFRC) rates skylights for air leakage, condensation, heat loss, heat gain and visible signs of light transmitted. The NFRC certificate and label show that the manufacturer had the product tested and lists the results.
The International Code Compliance (ICC) offers an evaluation service (ICC-ES) that rates building products on many factors and issues a technical report. Skylights that have been evaluated by the ICC are placed on the ICC product list and can be promoted as "ICC listed."
Formerly the American Society for Testing and Materials, the organization changed its name to ASTM International as its standards became used around the world. ASTM International issues numbered standards which skylight manufacturers want to meet, such as ASTM E283 which measures air leakage, and ASTM E331 which measures water resistance.
Energy Star is a U.S. Department of Energy program that encourages manufacturers to make energy-efficient products. Skylights bearing the Energy Star label tell consumers that these skylights will save them money on their energy bills.