The system by which energy is produced and used is increasingly at the heart of the environmental and economic challenges facing the United States. Building energy codes provide an excellent example of how states can enact innovative efficiency policies to quell rising energy demand while meeting environmental goals. Effective September 1, 2001, Texas will begin statewide implementation of the latest version of the nationally-recognized building energy code The International Energy Conservation Code (IECC). IECC adoption represents a significant achievement for Texas by elevating statewide residential and commercial building efficiency standards to among the best in the nation. This report provides a foundation for understanding statewide building energy codes as a model efficiency initiative in the broader context of the current energy challenges and choices facing Texas and the United States. It also demonstrates that the adoption and implementation of the IECC building energy code in Texas can result in significant energy, cost, and environmental savings.