"Energy codes can vary greatly from state to state, and even from edition to edition of codes developed by the same authority. Some of the codes in place are state developed, and take into account state-specific concerns such as climate, the state's economy and history, and impact on local building communities. Many other states adopt state-specific amendments to the national model codes. The codes are not a static document and, while national model codes are published every 3 years, they are almost constantly under revision to improve compliance, implementation, and enforcement for everyone involved in the building process."

The BCAP's code status database tracks those changing codes. It looks as if there are other online resources in the works, as well, including the intriguingly-named "Code Builder."