Abstract: A structural insulated panel system includes a frame including a first vertical frame member and a second vertical frame member and a top frame member and a bottom frame member. A first siding member is attached to one side of the frame and a second siding member is attached to an opposite side of the frame to form a cavity and an insulation material is provided within the cavity. A tongue portion includes a projection formed from the first vertical frame member disposed laterally outward from one vertical edge of the first and second siding members. A groove portion includes a recess formed from the second vertical frame member disposed laterally inward from an opposite vertical edge of the first and second siding members, so that the tongue portion from one panel is configured to mate with the groove portion of another panel to provide an assembly of multiple panels.