Horizontally oriented insulated metal panel siding system

An insulated metal panel siding system for a structure, said structure having a frame including wall framing, said wall framing having a base and including vertical frame members, said siding system comprising:

• (a) an elongated base member installed proximate said base of said wall framing for said structure and extending across at least two said vertical frame members in said wall framing, said base member having a profile running laterally along the upper side thereof;
• and
• (b) an elongated insulated metal panel installed on said wall framing, said panel running horizontally across said vertical frame members and abutting said base member, said panel having a rigid foam core, an interior metal facing, and an exterior metal facing, said panel having a profile running laterally along the lower side thereof;
• (c) wherein said upper profiled side of said base member substantially continuously abuts said lower profiled side of said panel, said base member upper profiled side and said panel lower profiled side being adapted to allow said base member and said panel to be joined by a tongue-in-groove joint running horizontally across said wall framing.