A US patent describes a roof system comprising a structural deck and polyisocyanurate insulation using a PIN flame retardant to achieve ASTM E-84 fire safety performance as well as roof waterproofing.
The foam insulation uses a non-halogenated, phosphorus-based, reactive FR (DEHMP diethyl hydroxymethyl phosphonate at 2-5% loading) to achieve ASTM E-84 (flame spread and smoke density, Steiner Tunnel) and E1354-11b equivalent or better than with the halogenated FR TCPP. Other possible P-FRs cited are organo-phosphates, organo-phosphites, organo-phosphonates, such as dialkyl hydroxyalkanephosphonate or diaryl hydroxyalkanephosphonate. The fire performance of the polyisocyanurate foam is indicated as resulting from the polyisocyanurate chemical functionalities, small foam cell size, despite use of flammable foam blowing agents.
“Roofing systems and roofing boards with non halogenated fire retardant”, US Patent n° 20150354220 of 27 December 2016, M. Nandi, L. Wang, J. Asrar, Johns Manville http://patents.justia.com/patent/9528269