Insulated building panel

A thermally insulated building structure comprising two butted panels each including a laminate of exterior building material and interior building material with solid insulation between them characterized by:

• the exterior building material being shorter than the solid insulation creating a gap in the exterior surface to receive calking material;
• a pair of complimentary grooves formed in the insulation of each panel which extend lengthwise of an edge of the panel proximate the inner surfaces of said exterior and interior building materials and exposing a portion of said surfaces,
• the walls of each groove being substantially parallel,
• a rearward portion of each groove is remote from an inner surface of said exterior and interior building materials having a taper which intersects the closed end of the groove to render the dimension of the open end of a groove greater than the dimension of its closed end,
• splines for joining the two adjacent panels together located half in each groove of a butted panel, each spline being tapered at one corner to facilitate its entering into the groove and to firmly mate with the taper at the closed end,
• screws inserted through the exterior and interior building materials directly into the splines to pull them toward the insulation engaging surfaces of the exterior and interior building material.