The aim of this paper is to develop a new concept of sketch tools for the very steps of the design process. The originality lies in the use of optimization to define a global design of the building, the energy system and the control strategy. Therefore, an adapted model of the building has been realized, not directly using fine dynamic models (like those that can be found in tools TRNSYS, DOE2.2 and EnergyPlus...), but more coarse equations adapted to the sketch design phase. Those models are based on static and macroscopic equations investigating energetic and financial balances. In order to optimize the global cost, this model will be used coupled with optimization techniques. An application of an energy positive railway station will be presented demonstrating that it is possible to make a global sketch design (size and characteristics of the walls of the building + size of the energy systems + optimal control strategy over a typical day) extrapolating over a 30 years cycle of live of the building.