Patent ID: 7972688

Claim:
A covered low-slope or flat roof comprising: (a) a roof deck; (b) an insulation board including a polyurethane, a polyisocyanurate, or a mix of polyurethane and polyisocyanurate cellular structure, said insulation board having a density that is less than 2.5 pounds per cubic foot, and said insulation board having a first planar surface and a second planar surface, said first planar surface and said second planar surface each having a facer positioned adjacent thereto; (c) a coverboard including a polyurethane, a polyisocyanurate, or a mix of polyurethane and polyisocyanurate cellular structure, said coverboard having a density greater than about 2.5 pounds per cubic foot and less than 6 pounds per cubic foot, an iso index of at least 175, and a first planar surface and a second planar surface, said first planar surface and said second planar surface each having a glass facer positioned adjacent thereto; and (d) a polymeric membrane, wherein said insulation board and said coverboard are between said roof deck and said polymeric membrane.