Abstract: This panel unit consists of several boards, driven together, which are fastened to each other, in the preferred manner of tongue-and-groove boards, and with an insulation mat applied to one side of the boards, distinguished in that fastening connected across the long axis of the boards and fastened thereto, and that the insulation mat is glued onto this side of the panel unit. The fastening strips have offsets at their ends, of different offset depths on each end, these fastening strips being connected together at their meeting ends, forming spacing accommodating the insulation mat.