In January 2011, I shared NRCA's concerns regarding how installation of rack-mounted photovoltaic (PV) systems may affect roof assemblies' fire classifications. At that time, Underwriters Laboratories (UL) Inc. was determining the fire classifications of rack-mounted PV systems separately from the fire classification determination for roof assemblies using UL 790, "Standard Test Methods for Fire Tests of Roof Coverings." Research testing of rack-mounted PV systems in combination with roof assemblies showed flame spread results significantly greater than when the two components were tested individually.
UL has since incorporated a revised fire classification test method within UL 1703, "Flat-Plate Photovoltaic Modules and Panels." Using UL 1703's October 2013 and subsequent editions, rack-mounted PV systems are tested in combination with representative roof assembly specimens.
The effective date for the new version of UL 1703 is Oct. 25, 2016. Until that date, PV panels still are permitted to be classified using UL 1703's previous fire test methods of testing PV panels and roof assemblies individually.
The new edition of UL 1703 is incorporated into and will be required for compliance with the International Building Code,® 2015 Edition and International Residential Code,® 2015 Edition.