Technological innovation and architectural design are getting closer than ever. Technological innovation and architectural design are getting more unified defining the building envelope as a fusion of these two elements. The architecture´s skin loses its function of pure cladding to become an interface: the building receives and transmits information in an “intelligent” way. The door of 4.1 project appropriates this technology and has been thought and designed as an architectural item. The internal ribbed aluminium structure can be covered with wood or lacquered panel. A layer that knows how to protect but also how to express.