Energy Efficient Building (EEB) design requires many simulation tools to support making decisions for optimized building solutions, resulting in frequent interactions between computational tools. Building Information Modeling (BIM) server platforms can support the storage, maintenance, and query of IFC-based building information models. However, the lack of a unified interface to support information exchange and interoperability among different building design and simulation tools has become a bottleneck of the EEB design process. This paper describes an integrated approach at the data level to combine BIMserver and OpenStudio to build a unified EEB data exchange model. Our first step is to build an information exchange bridge between BIMserver and OpenStudio which will enable different design and simulation tools that are connected to either of them to interoperate and exchange needed data. In the paper, we also discuss the challenges of the seamless integration due to the dependency on both BIMserver and OpenStudio. The integrated approach, which organizes the data flow in a unified model, enabling effective exchange of data, is currently in a beta-testing phase.