A new method for an integrated design of process furnaces (especially tubular fired heaters) has been developed. This approach consists in bridging a gap between equipment (furnace) design and process design. It utilizes some principles from Pinch Analysis. The procedure for an efficient integration of furnaces is partly interactive and is based on three stages: (i) targeting, (ii) synthesis and (iii) detailed design. Its application is illustrated through examples - case studies for both grassroot design and retrofit. A substantial energy saving can be observed.