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Codes 101

What are Building Energy Codes?

Energy codes are holistic minimum energy efficiency requirements and additional energy efficiency building design provisions for new building construction (residential single-family, residential low, mid, and high-rise multifamily, commercial, institutional, industrial) and particular building renovations. The primary impetus for building energy codes is achieving energy efficiency, reducing emissions, and saving consumer costs. State and local building energy codes are based on the “model codes,” which are the International Energy Conservation Code (IECC) and ANSI/ASHRAE/IES Standard 90.1-2019 (ASHRAE). The model codes are updated on a three-year cycle.

What Do Building Energy Codes Provide

  • Consistent minimum legal construction provisions across the adopting jurisdiction.
  • Drive higher performance building practices throughout the construction industry, influencing and ultimately defining standard practice.
  • Building energy codes present one of the most cost-effective ways of reducing energy consumption in new construction and substantial renovations.
  • Save energy and reduce emissions, assure better indoor air quality, prevent mold and flame spread, and provide a more resilient structure during adverse events.

Building Energy and Consumer Cost Savings

Energy codes are a significant driver of building energy and consumer cost savings. They are seen as a critical tool to cost-effectively reduce emissions in the built environment and help mitigate the effects of climate change. DOE analysis of each model code has consistently demonstrated that investing in energy efficiency during new construction or renovation of existing buildings is cost-effective and produces significant lifetime savings for the building owner and occupant. When estimating their impact over decades (2010-2040), energy codes are projected to save $138 billion in energy cost savings, 900 million metric tons (MMT) of avoided CO2 emissions, and 13.5 quads of primary energy. In addition to energy savings, energy codes improve occupant comfort, building resilience, and indoor air quality.

Defining Energy and Cost Savings

DOE is required by law to analyze each version of the code (IECC and Standard 90.1) to determine whether the updated codes and standards are more efficient than the previous edition. Assuming the determination is positive (i.e., the new edition is more efficient), a new model energy code is established and recommended for state and local adoption. The most recent determinations:

  • Residential Model Code - 2021 International Energy Conservation Code (IECC)
    • Determination: 9.38% site energy savings (compared to 2018 IECC)
    • Application: Residential one-and-two-family dwellings and multifamily three stories or fewer
  • Commercial Model Code - ASHRAE Standard 90.1- 2019
    • Determination: 4.7% site energy savings (compared to Standard 90.1-2016)
    • Application: Commercial and multifamily four stories and greater

History of Energy Codes

The national model energy code was first introduced through the Energy Conservation and Production Act (ECPA) of 1975, adopted in response to the 1973 oil embargo. ASHRAE 90-1975 was the first national model energy code covering residential and commercial buildings. After that, the national model code was updated periodically, not on a three-year cycle - as it is today - until the early 2000s. As shown in Figure 1, the estimated reduction in energy use from that very first code to the current national model codes - the 2021 IECC and ASHRAE 90.1-2019 - is approximately 50%.

The graph below outlines the estimated national average energy use reduction in model energy codes from 1975 to the present. Green down arrows indicate a more efficient code, while red up arrows indicate lost efficiency from code to code. The data presented in this graph is based on total building energy use. Click on the figure to access an interactive version of this graph on BECP’s Tableau Public page.

Figure 1: Estimated Improvement in Residential and Commercial Energy Code