A breathing circuit (100) including an airflow conduit (110) configured to receive gas at input end and configured to deliver the gas to a patient at an output end, a heating element (129) disposed inside the airflow conduit configured to heat the gas inside the airflow conduit between the input end and the output end, a removable sleeve comprising a heat shield (200), and an outer conduit (400). The removable sleeve comprises an infrared shield and is disposed between the heating element and an outside surface of the airflow conduit such that the heat shield prevents energy loss and radiant energy loss from within the airflow conduit. The outer conduit houses the airflow conduit. An evacuated air gap (440) is disposed between the outer conduit and the airflow conduit.
