Abstract: The present invention is an insulated modular wall system for quickly and efficiently constructing buildings of one or more stories. Included in this modular wall system is a plurality of building pans, each having a pair of flanges for interlocking adjacent building pans. Some of these flanges are configured to compensate for dimensional variations that are inherent in each of the building pans. If not compensated for, these dimensional variations can result in excessive stress when a plurality of adjacent building pans are interlocked. Included in the invention is a unique method for supporting convention floor boards, and a unique arrangement for creating a gap for electrical wires and the like.