How can we sustainably reduce the carbon footprint of buildings? One of the keys lies in the digital building infrastructure as a “nervous system” that enables efficient control and has a high priority throughout the entire life cycle of a building - far beyond the construction phase. Using a comparison of CAN bus from the automobile and KNX in the building, we highlight the importance of interoperability (which means we speak one language) as the DNA for diversity in products, technologies and applications.