Proposing initial ideas for zero energy buildings is a difficult task. Various existing BPS tools have been proposed and are used to support the design of zero energy buildings during later design stages. However, this is when many detailed decisions about the design have already been taken. There is a growing awareness to integrate BPS tools in the design process during early design phases. This is one of the main objectives of that we adopt here to develop a suggested decision tool. In this paper, we specifically discuss the realization of a tool for early architectural design of zero energy housing. The paper presents the first prototype of this tool that has been tested with different volunteers to see how they react. A major focus of his work is the graphical user interface. We describe the interface development process, the resulting prototype and its performance for initial design conception of different zero energy housing typologies. We also identify direction for future development of the tool.