Whether or not it is enforcing a locally adopted code or has no code at all, a city can completely avoid state regulation of one- and two-family dwellings in its jurisdiction by opting out of the statewide standards. This can be accomplished by a specific and recurring resolution process. This requires a city to pass a resolution by a two-thirds vote of the governing body exempting one- and two-family dwellings in its jurisdiction from the applicability of the statewide standards and to forward the resolution to the state fire marshal. The resolution, however, expires 180 days following the date of the next election. Hence, each new governing body must pass a subsequent resolution to continue avoiding applicability of the state standards.
Citation from Tennessee State Fire Marshal's Website:
On June 25, 2009, Governor Phil Bredesen signed SB 2300 (now Public Chapter 529), placing residential energy efficiency codes under the purview of the State Fire Marshal, who shall select the specific ICC code edition to be implemented. In 2017, the Fire Marshall oficially adopted the 2012 International Energy Conservation Code. The codes provisions of Public Chapter 529 also include a mechanism through which local legislative bodies can "opt out" their communities with a two-thirds vote. Additionally, for communities that have somewhat outdated codes programs, the state will provide incentives in the form of free training and materials to encourage them to update their standards.