A joint is made from first and second vacuum spool pieces connected end to end. Each spool piece includes an inner conduit surrounded by and spaced from an outer jacket. Each outer jacket includes an expansion-contraction portion adjacent each end thereof. Each end portion of each jacket has a first member in sealing contact with a mating second member on the inner conduit for retaining a vacuum in the annular space. After two spool pieces are joined, the first and second members are shifted relative to one another so as to preclude any direct conductive heat leak path and permit the vacuum in the annular space of one spool piece to communicate with the vacuum in the annular space of the other spool piece.