Since 2000, the I-Codes have served as models for almost all state and local building codes in the United States. The 2012 edition of the I-Codes includes several landmark advances in building energy efficiency and sustainability. Not only does the 2012 International Energy Conservation Code (IECC) include new and higher thermal standards for almost every roof and wall assembly, but these standards are further increased in the new International Green Construction Code (IgCC), which is intended to serve as an overlay code, or “above the code” standard for sustainable buildings. (For an overview of the I-Codes, see “Model Codes 101” on page 28.)