A roof assembly comprising a sheet of roof membrane and an insulation board assembly, the insulation board assembly comprising: a foam insulation board having first and second opposing surfaces; a top facer attached onto a top side of the foam insulation board, the top facer being made of woven material having a warp density from 4 to 30 ends per 25.4 mm (per inch) or a weft density from 4 to 30 picks per 25.4 mm (per inch) and a tensile strength greater than 356 N/76 mm (80 lbf/3 inch) in both a machine direction and a cross direction and a tongue tear strength of over 67 N (15 lbf) in both a machine direction and a cross direction; and a bottom facer attached onto a bottom side of the foam insulation board, the bottom facer being made of woven material having a warp density from 4 to 30 ends per 25.4 mm (per inch) or a weft density from 4 to 30 picks per 25.4 mm (per inch) and a tensile strength greater than 356 N/76 mm (80 lbf/3 inch) in both a machine direction and a cross direction and a tongue tear strength of over 67 N (15 lbf) in both a machine direction and a cross direction, wherein the woven material is made of yarns or tapes made of polyethylene, ethylene alpha-olefin copolymers, polypropylene or propylene alpha-olefin copolymers, wherein the woven material has a weight from 40 to 200 grams per square meter, and wherein the woven material has a thickness of 0.05 mm (2 mil) to 1.3 mm (50 mil), and wherein the sheet of roof membrane is an EPDM (ethylene-propylene-diene-monomer), TPO (thermoplastic polyolefin), PVC (polyvinyl chloride) or KEE (ketone ethylene ester) roof membrane with a non-woven fleece laminated on the back side and adhered to the insulation board assembly, wherein the roof assembly meets the Very Severe Hail rating of FM 4470 (Class 1). a foam insulation board having first and second opposing surfaces; a top facer attached onto a top side of the foam insulation board, the top facer being made of woven material having a warp density from 4 to 30 ends per 25.4 mm (per inch) or a weft density from 4 to 30 picks per 25.4 mm (per inch) and a tensile strength greater than 356 N/76 mm (80 lbf/3 inch) in both a machine direction and a cross direction and a tongue tear strength of over 67 N (15 lbf) in both a machine direction and a cross direction; and a bottom facer attached onto a bottom side of the foam insulation board, the bottom facer being made of woven material having a warp density from 4 to 30 ends per 25.4 mm (per inch) or a weft density from 4 to 30 picks per 25.4 mm (per inch) and a tensile strength greater than 356 N/76 mm (80 lbf/3 inch) in both a machine direction and a cross direction and a tongue tear strength of over 67 N (15 lbf) in both a machine direction and a cross direction, wherein the woven material is made of yarns or tapes made of polyethylene, ethylene alpha-olefin copolymers, polypropylene or propylene alpha-olefin copolymers, wherein the woven material has a weight from 40 to 200 grams per square meter, and wherein the woven material has a thickness of 0.05 mm (2 mil) to 1.3 mm (50 mil), and wherein the sheet of roof membrane is an EPDM (ethylene-propylene-diene-monomer), TPO (thermoplastic polyolefin), PVC (polyvinyl chloride) or KEE (ketone ethylene ester) roof membrane with a non-woven fleece laminated on the back side and adhered to the insulation board assembly, wherein the roof assembly meets the Very Severe Hail rating of FM 4470 (Class 1).