Make sure all cantilevered floors are capped and sealed on the underside.
The picture shows a cantilevered floor area that will need to be draftstopped. The reason it is draftstopped is because there is an air conditioned interior floor space above this cantilever. If left un-insulated and not draftstopped, this would become a drafty location in this room upstairs. This is typically required to be insulated by building codes in most jurisdictions. The proper way to install draftstopping here is similar to the installation on the inside of the house behind the tubs and in concealed areas.