This paper investigates the complex design process for sustainable buildings mediating between spatial composition and architectural typology on one side and thermal, climatic conditions and energy use on the other hand. The theoretical base is Hermès V Le Passage du Nord-Ouest(Serres, 1980) by the French philosopher and mathematician Michel Serres (1930 -), where he is searching for a passageway from the exact sciences to the arts and humanities. While both are looking to explain the world with their own methods, they are turning their backs at each other. The shipping passage in the North of Canada connecting the Atlantic and the Pacific serves him as a metaphor for this complex thought space linking, connecting and dividing, these two explanations of the world. This text is dealing with the connection of places, which seemingly are separate: rigidness and phantasy, myths and exactness, quantitative and qualitative knowledge. Based on this understanding the paper analyses the design process between architecture and engineering as a passage passing four overarching theoretical frames crossing between geometry and perception, drawing and material, atmosphere and typology, technology and desire thus befriending quantitative and qualitative methods of design thinking. The research analyzes a built experiment, the Interlock House, which focused on the relationship of spatial composition and air flow as a means of energy transfer, the impact of passive and active environmental controls and systems on architectural design and improved building energy performance. The means to travel the passage: proportions, thermal detailing, natural ventilation strategies and daylighting are here identified as key moments for sustainable design. Design communication for sustainable buildings needs to convey information between multiple entities with opposing language systems and thus equals a map rather than a flow chart. A collaborative design methodology emerges from these passages when the ice breaks.