This map, from the U.S. Department of Energy, shows minimum residential building code levels (roll over each state for more information). The International Energy Conservation Code (IECC) is the national energy code standard. If every state adopted the 2012 edition, it would result in about $40 billion annual energy savings by 2030, and 200 million metric tons of carbon dioxide emissions avoided every year, according to an analysis by the Alliance to Save Energy.