Abstract: A prefabricated building panel includes first and second side panel members. A thermally insulating core is disposed between those side panel members. A first panel end surface includes a pair of spaced projections defining a channel-way. A second panel end surface includes a pair of spaced channels and a thermal barrier plug. Two adjacent building panels may be interconnected by engaging the pair of spaced projections at the first end of the first panel in the pair of spaced channels in the second end of the second panel while simultaneously engaging the thermally insulating plug at the second end of the second panel in the channel-way at the first end of the first panel.