The following organizations provide building energy code information:

Building Codes Assistance Project - BCAP
BCAP is a not-for-profit organization working to save energy in homes and buildings by promoting the adoption and implementation of building energy codes. BCAP provides free assistance to states and municipalities in their efforts to adopt and implement both commercial and residential energy codes. BCAP also functions as a clearinghouse of information about building energy codes and other measures for saving energy in homes.

U.S. Department of Energy - Status of State Energy Codes
To view the status of a particular state's residential energy codes, select the state you are interested in.