This paper describes research on a computer model for building energy simulation. The main goal of this effort has been to provide building designers a better design tool for energy optimization in their building design processes. With the rapid development in computing technology, today's expectation for computer-aided building design (CABD) systems have matured to an advanced level-to the point where designers are open to the idea of computers helping them in the thought process and not just being used to manipulate and represent geometric shapes [J. Pohl et al., 1992. A Computer-Based Design Environment-Implemented and Planned Extensions of the ICADS Model, Design Institute Research Report, CADRU-06-92, California Polytechnic State University, San Luis Obispo, CA.]; [J.A. Clarke, A.D. Irving, 1988. Building Energy Simulation: An Introduction, Energy and Buildings, 10 (1988), Elsevier, pp. 157-159.]. By its very nature, design is a multidisciplinary and creative activity which encompasses all the relevant areas to be considered during the design process. Thus, the CABD system of today is expected to be a general purpose integrated system, rather than a domain-dependent isolated graphics system [J. Pohl, L. Myers, A. Chapman, J. Cotton, 1989. ICADS: Working Model Version I, Design Institute Research Report, CADRU-03-89, California Polytechnic State University, San Luis Obispo, CA.]. This research effort embodies a prototype interface system for a building energy simulation model (EWERife). This interface system is not a simple layer between user and simulation model, but rather, a general interface strategy to control simulation models and relevant databases to be integrated into CABD. The system includes a user interface module, system interface module, general database handling module, automated input processor, building matrix system, and a result analysis and recovery system.