Building design is an iterative process from the conceptual design up to the final process, so the use of computer-based tools here is vital. The purpose of this research was to investigate the most popular tools for building design and present a framework of an optimization model for building envelope, without compromising on energy efficiency, comfort, cost, and environment. The combination of simulation tools DesignBuilder, SimaPro and the method of multiple criteria complex proportional assessment (COPRAS) were not implemented in researches yet. Following the model, we determine the values, which are usually chosen as the optimization criteria: energy demand (heating, cooling, electricity), comfort parameters (PVM, PPD values, discomfort hours, daylight), embodied, operational energy, CO 2 emission, investment and exploitation cost. As the result, the use of this optimization model does not require great experience, but improve and facilitates the building design process.