2021 International Energy Conservation Code (ICC IECC-2021)

Wood home with greenery adhering to best International Energy Conservation Code (IECC) requirements.

In our solar system, energy begins with the sun. The core’s extreme pressure—250 billion atmospheres—and temperature—15.7 billion kelvin—drives fusion, resulting in a decrease in mass and a release of energy. These photons leave the sun, but they take their time, colliding for anywhere from 10,000 to 170,000 years. Once they enter space, eight minutes pass before the photons meet the earth, thereby driving our planet’s energy, water, biochemical and other cycles.

The buildings sector accounts for around 76% of electricity use and around 40% of all US primary energy use. In an industrialized world, conserving energy in buildings is essential to meeting global challenges like anthropogenic climate change. For this reason, the International Energy Conservation Code (IECC) is adopted in most US states. Its current edition is ICC IECC-2021.

About The International Energy Conservation Code

Developed and published by the International Code Council, the 2021 International Energy Conservation Code, or ICC IECC-2021, through prescriptive and performance-related provisions and broad-based principles, sets the minimum requirements for energy-efficient buildings.

Energy use faces numerous influences. Maintaining energy-efficient practices isn’t as simple as regulating HVAC, electrical, and plumbing systems, although these are important factors. Roof and wall insulation R-factors and window and door thermal transmittance (U-factors) are essential to achieving a vigorous building envelope. Climate also has a major impact on energy use, so it is essential to comprehend the significance of the climate zone a building is located in to drive energy efficiency.

2021 IECC Chapters and Appendices

To address these interests, the IECC document contains sections focused on administration and definitions (Chapters 1-2), climate zones and general materials requirements (Chapter 3), energy efficiency requirements (Chapter 4), requirements for existing buildings (Chapter 5), and referenced standards (Chapter 6).

ICC IECC-2021 contains two separate sets of provisions, known as IECC—Commercial Provisions and IECC—Residential Provisions, each of which are broken up into the chapters mentioned above to address buildings within their respective scope.

ICC IECC-2021 also contains several appendices, which, while not part of the code, can become part of the code when specifically included in the adopting ordinance.

Appendices CA and RA support of Chapter 1 of ICC IECC-2021, which requires the establishment of a board of appeals to hear appeals regarding determinations made by the code official. These two appendices provide qualification standards for members of the board and its operational procedures. Appendices CB and RB address provisions for solar capacity in new structures, and Appendices CC and RC provide requirements intended bring about net zero annual energy consumption in commercial buildings and residential buildings, respectively.

Who Needs ICC IECC-2021?

The IECC’s requirements serve as the basis for laws and regulations throughout the US and in other countries, and this is typically the use of the code document. In fact, the International Energy Conservation Code is adopted in most US states for commercial buildings, residential buildings, or both.

Please note that the IECC and another standard, ANSI/ASHRAE/IEC 90.1, serve as the main baseline energy conservation codes. In result, many states that have not adopted an edition of the IECC have adopted ANSI/ASHRAE/IEC 90.1, while some do make use of both.

You can learn more about the ANSI/ASHRAE/IES 90.1-2019: Energy Standard For Buildings standard here and see a list of all state building energy code adoptions listed here.

The International Energy Conservation Code is also used in a variety of nonregulatory settings. This includes voluntary compliance programs supporting sustainability and energy efficiency, the insurance industry, facilities management, best practices benchmarks for designers, textbooks and curricula, building design and construction reference works, and in the certification process for buildings and individuals.

Changes to ICC IECC-2021

The 2021 IECC revises the 2018 edition of the code, and the changes made to both the residential provisions code and the commercial provisions code represent major energy efficiency gains in constructing and renovating homes and reducing carbon emissions in commercial buildings.

Below are some changes made to IECC residential provisions:

  • The R-value of wood frame insulations increased in Climate Zones 4 and 5.
  • The R-value and depth of slab edge insulation were increased in Climate Zones 4 and 5, and slab edge insulation is now required in Climate Zone 3.
  • Ceiling insulation was increased in numerous Climate Zones.
  • Fenestration U-factor was for Climate Zones 3 and 4, and the area-weighted maximum fenestration U-factor was decreased in all Climate Zones.
  • The efficacy value of high-efficacy lamps was increased.
  • Provisions for installing exterior lighting controls were added.
  • The duct testing exemption for ducts in conditions space was removed.
  • Compactness Factor was added to the Performance Path for hot water usage.
  • The climate zone map was updated to align with ASHRAE 169, and a cap was placed on the amount of available onsite renewable energy at 5% of total energy use.
  • Maximum ERI target scores were reduced.
  • New Appendix RC for Zero Energy Residential Building Provisions.

Changes on the IECC commercial provisions side:

  • Requirement was added for the thermal envelope certificate that includes R-values, U-values, and building envelope air leakage testing results.
  • Numerous updates to better align with ASHRAE 90.1, including changes to:
    • Roof assembly performance
    • Above-grade wall assemblies
    • Below-grade wall assemblies
    • Insulation requirements for floor assemblies
    • F-factors for unheated slabs
    • Vertical fenestration SHGC (Solar Heat Gain Coefficient) requirements
    • Skylight U-factor and SHGC requirements
  • “Roof Gardens” was changed to “vegetative roof” to align with other I-Codes.
  • Definition of “wall, above grade” was modified to include:
    • Between-floor spandrels
    • Peripheral edges of floors
    • Roof and basement knee walls
    • Dormer walls
    • Gable end walls
    • Walls enclosing mansard roofs
    • Skylight shafts.
  • “Non-swinging doors” R-value requirements were deleted and added as U-factors.
  • Requirement for horizontally hinged doors with a single row of glazing were added.
  • Air leakage testing requirements were added for Class R and Class I occupancies.
  • ASTM E3158 was added as an approved testing method.
  • Efficiency requirements were added for small fans.
  • Modifications were made for energy credits.
  • New Appendix CC for Zero Energy Commercial Building Provisions.

Please note that these examples do not fully detail the expanse of revisions made to ICC IECC-2021. Users can note where technical changes have occurred from the 2018 edition through solid vertical lines in the margin of the body of the code document, along with other indicators.

You can also refer to the US Department of Energy’s presentations detailing 2021 IECC Commercial Building Provisions changes and 2021 IECC Residential Building Provisions changes.

ICC IECC-2021: 2021 International Energy Conservation Code is available on the ANSI Webstore.

Other International Code Council Codes (I-Codes)

Users of the International Energy Conservation Code should be aware that requirements in other codes can have an impact on energy conservation. Thankfully, the IECC is fully compatible with all other International Codes (I-Codes) published by the International Code Council. This includes:

ICC IBC-2018: 2018 International Building Code (You can learn more in our post 2018 International Building Code (ICC IBC-2018))

ICC IEBC-2018: 2018 International Existing Building Code

ICC IFC-2018: 2018 International Fire Code

ICC IFGC-2018: 2018 International Fuel Gas Code

ICC IMC-2018: 2018 International Mechanical Code

ICC IPC-2018: 2018 International Plumbing Code

ICC IPMC-2018: 2018 International Property Maintenance Code

ICC IPSDC-2018: 2018 International Private Sewage Disposal Code

ICC IRC-2018: 2018 International Residential Code

ICC IWUIC-2018: 2018 International Wildland-Urban Interface Code

ICC IZC-2018: 2018 International Zoning Code

ICC PC-2018: 2018 ICC Performance Code for Buildings and Facilities

You can acquire the 2021 IECC along with all these other I-Codes as the ICC International Building Code Package (IBC).

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