This paper presents a CAD transfer method to visualize thermal simulation results in a virtual environment in order to optimize building design determined by energy efficiency. As the goal is to present a more immersive thermal simulation and to project the calculation results in projective displays particularly in cave automatic virtual environment, the main idea of the method is to provide a workflow so that the thermal result can be visualized and simulated in the virtual environment (VE). The paper shows the experiment results conducted in an immersion room by some respondents. An evaluation of the method has demonstrated that it is possible to conduct a specific data workflow in order to represent building performance data and particularly thermal simulation results in virtual reality (VR). With this method, the data flow that starts from the design process is completely and accurately channeled to the VR system. CAD data in 3D mock-up models composed of basic geometry are usually designed and transferred to other tools particularly if intended for VR. However, CAD data needed for the VE is not simple, it needs to be structured in a workflow method. Challenges in data exchange and interoperability among design, simulation and VR tools used have become an important issue to investigate how the workflow works