State Code Adoption Tracking Analysis

The U.S. Department of Energy (DOE) Building Energy Codes Program reviews adoption of energy codes for residential and commercial buildings. State adoption is reviewed based on the national model energy codes–the International Energy Conservation Code (IECC) for residential buildings and Standard 90.1 for commercial buildings (42 USC 6833). DOE analyzes state energy codes to assess the savings associated with code updates. The resulting findings aid model code adoption, and serve as a means of supporting states working to update their energy codes.

State Analysis

Pacific Northwest National Laboratory (PNNL) conducts state-level technical analysis based on a methodology established by DOE. PNNL reviews state energy codes based on the IECC and Standard 90.1, including any significant amendments. This helps states understand how their codes compare to the national model codes and provides a portrait of national code adoption.

A quantitative analysis is performed to assess the energy savings impacts within a given state, resulting in an energy index. For residential, the Energy Index represents the ratio between the whole-building site energy intensity of a state code and that of the 2006 IECC. The underlying energy use intensities (kBtu/ft2-yr) are derived from per-dwelling unit intensities (kBtu/unit-yr) which are aggregated across building types, foundation types, system types, and climate zones using weighting factors based on new-housing permits. For commercial, the Energy Index represents the ratio between the whole-building site energy intensity of a code and that of 90.1-2004. The underlying energy use intensities (kBtu/ft2-yr) are derived from per-building intensities (kBtu/building-yr) which are aggregated across building types and climate zones using weighting factors based on new-building permit data.

This comparison allows for a categorization of each state, with categories based on recent editions of the model codes. Any code for which the Energy Index is not more than 1% higher than that of an IECC or Standard 90.1 edition is considered equivalent to that code edition. For states whose codes fundamentally differ from the national model codes, PNNL may consider analysis conducted by others as a basis for its categorization.

Why not show EUI directly instead of an Energy Index relative to the 2006 IECC? There are two primary reasons. First, the Index value is easier to interpret because it directly shows relative performance (i.e., as a fraction or percentage of the 2006 baseline). Second, the EUI values tend to change a bit from year to year (or quarter to quarter) due to improvements in the EnergyPlus simulation tool, bug fixes in DOE's simulation infrastructure, updated site-source conversion factors, differences in construction weighting factors, etc. Index ratios between a given code and the 2006 IECC tend to change much less in such situations, so they avoid the appearance of a state code's performance changing when the state didn't change its code.

In an effort to simplify the maps, the categories were changed and no longer include “between categories” (e.g., Between 90.1-2010 and 90.1-2013) or the words “or equivalent”. The current residential categories include: No statewide code, < 2009 IECC, 2009 IECC, 2012 IECC, 2015 IECC, and 2018 IECC. The current commercial categories include: No statewide code, < 90.1-2007, 90.1-2007, 90.1-2010, 90.1-2013, and 90.1-2016. With the implementation of these changes, several states now fall into different categories than in previous maps.

*A review of the codes in place in jurisdictions across the state indicates that 86% (Hawaii) and 82% (Arizona) of the population is covered by codes at this level.

^ When an amendment impacting energy efficiency can be quantified using DOE Prototype Building Models, they were captured in the analysis.

Note:

1. A home rule state is one where codes are adopted and enforced at the local level. Some home rule states will have a mandate that jurisdictions can go above code but also have to meet a certain minimum code. In general terms, the idea of home rule is defined as the ability of a local government to act and make policy in all areas that have not been designated to be of statewide interest through general law, state constitutional provisions, or initiatives and referenda.
2. States with extensively different baseline codes for which conducting custom analysis would be cost prohibitive and out of scope of this analysis.
3. For states adopting both IECC and 90.1, the IECC code is usually analyzed as the state current code in this study except for states with extensive amendments to the IECC.

*A review of the codes in place in jurisdictions across the state indicates that 86% (Hawaii) and 82% (Arizona) of the population is covered by codes at this level.

Available Data

The state-level results behind the DOE adoption status maps are available for commercial & residential buildings:

Commercial

Residential

More information on DOE support for state code adoption and other forms of technical assistance.