A mould housing (1) for apparatuses for expanding plastic containers, comprising at least two mould parts (2) which can be assembled together and which in an assembled state have an interior space for accommodating the plastic container that is to be expanded, and comprising at least one insulating element (6) which can be placed against an outer wall of at least one mould part (2). According to the invention, the insulating element (6) has a curved profile, wherein the curvature of the insulating element is matched to a curvature of the outer wall (15).