This paper demonstrates a simple and practical simulation-based approach for fast identification of appropriate building design strategies at the early stage of a design project. A simplified passive solar house was modeled using an integrated building energy and CFD simulation to examine the feasibility of different sustainable thermal strategies for use in the 2007 Solar Decathlon Competition. The home was modeled in EnergyPlus, and then the surface temperatures at times of interest were used as boundary conditions for CFD modeling in PHOENICS. A number of energy-efficient heating, cooling and ventilation strategies and technologies were tested. The simulation results confirmed some obvious conclusions but also showed that some design strategies that appeared to be promising and met typical design criteria failed to provide desired performance. The outcomes of this study are of great value for decision-making of appropriate architectural and engineering designs for the solar decathlon house. This study illustrates that an engineering-assisted design is feasible and helpful even at very beginning stage of a design project.