The building construction industry is the second largest industry in the U.S. as well as in the world. Yet it is the only significant industry that delivers its products to the market without first systematically testing them. It is no wonder that completed buildings rarely perform as intended in building design. Despite decades of efforts to make buildings more energy efficient, the lack of expected performance in buildings still usually includes energy. Building information models and modeling (BIM) is beginning to provide the basis for virtual testing of building performance. This talk describes the principles of BIM, energy performance related issues in modeling and model population with data, some of the critical "new generation" software, and great opportunities to improve critical processes in this industry that influence energy efficiency of buildings. It also describes LBNL involvement in the development of this new technology and how it can help make energy performance simulation and analysis become a mainstream and helpful means of making buildings factually more energy efficient.