The energy conservations codes are focused on the conservation of nonrenewable energy that is used to serve building occupants. In most places in the United States, building energy codes are based on either ASHRAE 90.1 Energy Standard for Buildings Except Low-Rise Residential Buildings (ASHRAE 90.1) or the International Energy Conservation Code (IECC). The IECC also references ASHRAE 90.1 as a compliance alternative for commercial buildings and for residential buildings with more than three stories. Federal law in the form of a U.S. statute requires local energy codes be at least as stringent as ASHRAE 90.1, which is referenced in federal law as the basis for federal programs. Both the IECC and ASHRAE 90.1 set energy efficiency provisions for new construction, additions, and new systems and equipment in existing buildings.