Composite, structural, insulative board

A composite, structural, insulated board for use in building construction, comprising:

• a multi-layered board construction comprising a core layer, a structural layer on one side of the core layer, and a facer layer on the opposite side of the core layer from the structural layer;
• wherein the core layer is comprised of graphite-infused polystyrene foam, wherein the foam is comprised of closed cells, and wherein the core layer has first and second core surfaces on opposite sides of the core layer respectively;
• wherein the structural layer has an inside layer and an outside layer, and the inside layer of the structural layer is laminated to the first side of the core layer, the structural layer having at least one ply of a first water resistant barrier layer adjacent a water resistant fiber board layer, wherein the fiber board layer comprises a laminate of a plurality of paperboard layers, wherein the farthest outside layer of the structural layer, on the other side of the structural layer from the core layer, is the first water resistant barrier layer, and further wherein the thickness of the structural layer is between about 1/32nd to ¼th of an inch and has a weight of 265-380 lbs. per MSF;
• wherein the facer layer is laminated to the second side of the core layer, wherein the facer layer has a second water resistant barrier layer as an outermost layer of the facer layer;
• wherein the first water resistant barrier layer is formed of a polyolefin,
• wherein the second water resistant barrier layer is formed of a polyolefin,
• and wherein the first and second water resistant barrier layers are formed of a housewrap material which is a microporous, monolithic or microperforated coating applied to a substrate.