The invention is related to a method of manufacturing a wall panel and a wall panel system. The method includes forming a glass-fiber reinforced cementitious layer including the steps of: pouring or injecting a slurry of uncured cementitious product into a mold, embedding glass fiber reinforcing material therein, and curing the cementitious product to obtain a cured cementitious product having a first side and a second side; and applying, to the second side of the cured cementitious product, an insulation layer, the insulation layer comprising a foam.