CertainTeed's FlintBoard® ISO NB is a high performance composite insulation board designed for steep-slope, slopes 3:12 or greater, roofing applications, where building's thermal boundary aligns with the roof deck. FlintBoard® ISO NB is composed of a closed cell polyisocyanurate foam core manufactured on-line to a fiber reinforced facer on one side and either OSB or plywood on the other. NB delivers the energy-savings and occupant comfort of highly thermal resistant insulation board with the added benefit of a nailable surface for steep-slope roof system installation such as shingles, standing seam metal, tile or slate. FlintBoard® roof insulation slows the flow of heat into and out of the building through the roof deck, reducing energy costs for building owners as well as thermal strain to the roof system. Composed of a closed-cell polyisocyanurate foam core, FlintBoard® offers the highest R-value (resistance to heat flow) per inch available and long-term thermal resistan...See Morece values (LTTR*) from 5.7 to 27, LTTR. FlintBoard® ISO NB is available in thicknesses ranging from 1.5" to 4.0". When manufactured online is available in 47.5" x 95.5" foam, bonded to 7/16" OSB; offline manufacturing yields 48" x 96" foam with substrate options including OSB, either 7/16" or 5/8" or plywood, either 5/8" or 3/4" CDX fire treated. FlintBoard® ISO NB is installed wood-side up, mechanically attached with approved fasteners. *LTTR is the industry standard method for calculating the 15-year time-weighted average for roof insulation. See Less