Building Codes Assistance Project

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.

Energy codes generally provide two methods for compliance. The first, and most common method (though, this tends to vary by locality) is referred to as the prescriptive approach. In this approach, a structure must be built to the prescribed insulation and other values found in the code. Trade-offs are allowed between certain building components that have different energy performances, giving an added degree of flexibility.

The alternative method of compliance is the performance approach. Using this process, a structure is allocated an energy budget, or total allowable energy use, and can use a combination of different insulation values and equipment efficiencies in order to meet this budget. The overall energy performance of the structure, and not the individual components, is what matters. For example, a builder can use less insulation but a more efficient furnace to meet the allocated energy budget for the structure.