A structural element for a housing structure of a heating device. The structural element is at least essentially, especially completely, developed as a foam part, preferably as a thermoplastic casting foam part. In addition, a housing structure is described, which has a corresponding structural element, preferably at least two corresponding structural elements. Moreover, a heating device is described that includes at least one corresponding structural element and/or a corresponding housing structure. In addition, a method for mounting a corresponding housing structure is described.