Underwriters Laboratories Inc. (UL) provides safety and performance testing for thousands of materials and products including both roof covering materials (e.g. shingles) and PV modules. Roofing systems undergo a suite of tests covered in UL 790 – Tests for Fire Resistance of Roof Covering Materials, the test standard that determines the fire resistance properties of roofing. All roofing systems undergo these tests as required by local and model U.S. building codes. Roofing systems that demonstrate the highest resistance to burning, burn through, and spreading of flames receive a Class A rating.
Materials with less resistance receive a Class B or C rating. Discussion of requirements for these fire class ratings are presented later.
PV modules undergo safety testing to another standard, UL 1703 – Flat Plate Photovoltaic Modules and Panels. While this standard describes a suite of tests designed to stress the module physically, environmentally, and electrically, it also subjects modules to a specific subset of UL 790 that results in determination of a fire rating for each PV module.