A building module for use in construction of a structure incorporating a plurality of said modules which together form at least part of the structure. Each building module comprises a first peripheral frame of a first size defining a space which receives a layer of barrier material, a second peripheral frame of a second size defining a space which receives a layer of barrier material and which is joined at a first junction to the first peripheral frame of the first size in abutting end to end relationship to form a first auxiliary module. A third peripheral frame has the same size as the first peripheral frame and which defines a space which receives a layer of barrier material. A fourth peripheral frame has the same size as the second peripheral frame and which defines a space which receives a layer of barrier material and which is joined at a second junction to the third peripheral frame of the first size in abutting end to end relationship to form a second auxiliary module. The first and second auxiliary modules are attached side by side to form said building module; wherein the first and second auxiliary modules are attached to each other so that the first and second junctions are staggered along the length of the structure.