Energy Codes

Energy codes are national model building codes that set minimum energy efficiency standards for many components in a new home, like lights, climate systems, insulation, windows, and more. The two most widely adopted energy codes are the International Energy Conservation Code (IECC) for single-family homes and ASHRAE’s Energy Standard for Buildings Except Low-Rise Residential Buildings (ASHRAE 90.1) for multifamily properties.

After an energy code is published once every three years, the Department of Energy compares the latest edition of the code to the previous edition to determine if the code has become more energy efficient. A positive determination by DOE triggers a series of requirements that are outlined in the DOE Determinations State Certifications Fact Sheet.

When a state or jurisdiction goes through the adoption process for an energy code, there are typically public hearings and an opportunity to amend the code prior to adoption. NAHB has developed a series of adoption kits that include highlights of changes from the previous code, associated cost increases and a list of suggested amendments.

Energy Code Adoption Cost Analysis

These cost studies quantify the economic impact of adopting specific energy codes and include the methodology used.

• 2021 IECC Cost and Energy Savings Analysis
• 2012 IECC Cost and Energy Savings Analysis
• Energy Code Percent Savings Calculation Methodology (White Paper)
• 2009 IECC Cost and Energy Savings Analysis
• NMHC Multifamily Methodology and Cost Charts
• NMHC 2009 to 2012 Cost Study Cost Study Charts

Energy Code Adoption by State

Most states adopt a statewide energy code that is an amended version of a national model code. This Adoption Summary Spreadsheet lists the current energy code in place for each state and describes the key amendments that were made to the model code along with a link to the amended version of the code. See the map below for a quick overview of IECC adoption status by state.

For more on the current IECC adoption cycle, see NAHB’s 2021 IECC Code Adoption Kit.