A prominent pathway for the aeronautical industry to meet contemporary challenges is to explore overall vehicular efficiency gains enabled by various functional and structural distributions and/or synergies between onboard systems. To that end, this paper combines analytical first-principle-based methods and principles of systems engineering and focuses on the Environmental Control System (ECS). The objective is to develop means for simple blank-sheet design of complete system architectures, which would help unlock potentially obscured parts of the system design space. Basic thermodynamics is employed, complemented with “Function-Behaviour-Structure-Experience” systems engineering framework. The method presented in the paper enables users to initialise the design from a primitive abstract system architecture described by elementary physical processes, and then carry out a sequence of decisions and design material systems architecture, i.e. concepts that respond to the system requirements. The preliminary results present development of architectures representative both of traditional pneumatic and innovative electrical ECS concepts. Energy consumption figures of merit (thermodynamic efficiency, exergy destruction rate) are used as guidelines during the design i.e. for a given flight condition, the designer can assess the influence of each choice on the overall system energy consumption. Trade-offs between architectural design choices and figures of merit are thus rendered transparent in preliminary architecture design. In this paper the figures of merit are based on thermodynamic energy efficiency; in perspectives the method can include other constraints such as e.g. weight, volume, cost, or other, with long-term objective of enabling a comprehensive multi-disciplinary multi-system aeroplane architecture design scheme.@en