Last updated October 7, 2013 

Adoption of Energy Codes

The following tables show a snapshot (as of November 4, 2013) of how many states and the corresponding populations have adopted the various versions of ASHRAE 90.1 and the IECC. The first table shows these stats for adoption while the second table shows them based on equivalent stringency. E.g. a state may have a state code that is equivalent to ASHRAE 90.1-2010 so that state (and the population for that state) would show up as 'None or Pre-2001' in the first table but 90.1-2010 in the second table.
The Purpose of Energy Codes*

Buildings have a fundamental impact on people’s lives, affecting their home, work, and leisure environments. In the United States, residential and commercial buildings together use more energy and emit more carbon dioxide than either the industrial or the transportation sector.

Fundamental environmental issues, as well as the increasing cost of energy, has elevated building energy efficiency to a key component of sound public policy.  While choosing less energy-efficient methods or materials may save money in the short term, it increases energy costs far into the future.  The potential long-term impacts of our choices result in a unique role for government in setting and ensuring compliance with building codes and standards, promoting improvements, and collecting and disseminating information on new technologies and best practices.

Building energy codes and standards set minimum requirements for energy—efficient design and construction of new buildings as well as additions and renovations of existing buildings that impact energy use and emissions for the life of the building.

Energy-efficient buildings offer both tangible and intangible energy, economic, and environmental benefits.

Energy-efficient buildings are more comfortable and cost effective.  
Lower energy expenditures often correlate with a reduced dependency on foreign oil, which impacts national security.  
Studies show a significant correlation in building energy use and environmental pollutants. 
Energy-efficient buildings can create economic opportunities for business and industry by promoting new energy-efficient technologies.  
While the marketplace does not guarantee energy-efficient design and construction, studies on operating costs and resale of commercial spaces built to higher energy efficiencies indicate direct savings to building owners and occupants and financial benefits to building owners."

*From the Lighting Development, Adoption and Compliance Guide of the DOE Building Technologies Program