A prefabricated wall module may include framing members and one or more insulations members. The insulation member may have pre-incisions, as made by a hot-wire, defining service fitting accommodations. The service fitting accommodations are accessible on the inside face of the insulation. The service fitting accommodations may be either or both of vertically or laterally extending, and are located in the same places in each module, the vertical locations being next to the studs, to which service fittings may typically be mounted, the lateral accommodations being at heights typical of switches and wall outlets. The insulation members may be supplied with tabs filling the accommodations. The tabs may be snapped out as required. The insulation members may have stud channels that are shallower than the studs, such that an air gap is established between the insulation and the internal gypsum board covering.