This nationwide analysis of commercial energy code compares ASHRAE Standard 90.1-2007 with the commercial code in each state as of June 2009. The results are provided in chapters specific to each state.

States with unique energy codes were not included in the analysis because the codes in these states would be difficult to appropriately compare to ASHRAE Standard 90.1 and most of these states have energy offices that routinely assess their codes against the model codes. In states with codes prior to and including the 2000 IECC or Standard 90.1-1999, those states with no statewide energy code, and home rule states which did not specifically request that another code be used, Standard 90.1-1999 was used as the baseline for comparison.

Three DOE Benchmark buildings were used for the simulation used in this analysis: a medium office building (53,600 ft²), a mid-rise apartment building (33,700 ft²), and a non-refrigerated warehouse (49,500 ft²)— representing ASHRAE Standard 90.1 non-residential, residential, and semi-heated requirements, respectively.

Locations for the analysis were selected based on obtaining a sample representative of each climate zone in the state, where typical meteorological year (TMY2) weather file locations existed, making sure to include the state capital. In the absence of a TMY2 weather file for a particular climate zone in a state, a representative location in an adjacent state was used for the purposes of the simulation.