An Example of a Collaborative Concept Development for Energy Positive Apartments. The Delft Prototype is a single apartment from a not yet realized Concept House Urban Villa, which consists of 16 apartments on 4 floors. Both the urban villa and the prototype demonstrate the characteristics of high level industrial production with an extremely low ecological footprint, as well as being energy-positive in use, and both are suitable for multi-storey housing. The research, development, production and built prototype resulted in a unique innovation on the Dutch building market a sustainable energy-positive apartment system for Skryť popis