Types

• IECC Air Barrier Requirements
  IECC requirements for a continuous air barrier in commercial buildings and air leakage limits for dwellings, with testing methods and the arithmetic of air changes.
• IECC Commercial Lighting Power and Controls
  IECC commercial lighting provisions covering lighting power allowances, automatic controls, daylight responsive controls, exterior lighting, and the two methods of calculating allowed power.
• IECC Envelope Insulation and Climate Zones
  IECC climate zones and insulation requirements for roofs, walls, floors, and slabs, with compliance paths and R-value and U-factor arithmetic.
• IECC Fenestration U-Factor and SHGC
  IECC requirements for windows, skylights, and doors, covering U-factor, solar heat gain coefficient, air leakage, NFRC ratings, vestibules, and glazing area.
• IECC Renewable, EV, and Electrification Readiness
  IECC provisions and related codes that prepare buildings for solar, electric vehicle charging, and electrification, covering reserved space, capacity, conduit, and additional efficiency credits.

Scope and application

• Covers the thermal envelope, air leakage, fenestration, lighting, mechanical systems, service water heating, and power for new buildings and for additions and alterations to existing ones
• Has separate commercial provisions (for commercial buildings and residential buildings of four or more stories) and residential provisions (for one- and two-family dwellings and townhouses up to three stories)
• Works with the IBC and IRC, which refer to it; the IEBC points to it for energy in alterations and additions
• ASHRAE Standard 90.1 is an accepted alternative path for commercial buildings
• Many states publish their own energy codes, based on the IECC or ASHRAE 90.1, with different edition dates
• Tables of values change with every edition, so these notes explain how to read and apply them and use few numbers

Editions and adoption

Always verify the adopted code edition and local amendments for the project jurisdiction.

Governing editions

• The 2024 IECC text could not be read directly; provisions here come from secondary summaries, from earlier notes in this wiki, and from adoption documents
• The 2024 IECC is estimated by DOE-affiliated analysis to be about 10 percent better than the 2021 edition for commercial buildings (a figure reported at about 10.6 percent site energy savings)
• The 2024 edition offers many options for design changes that earn efficiency credits (more than 50 according to one compliance guide), organized under the additional efficiency provisions of both chapters
• States adopt on their own schedules; many are on the 2021 or earlier editions, and some use ASHRAE 90.1 only for commercial buildings

Enforcement and administration

• The building official enforces the IECC through plan review and inspection; some states use a separate energy office
• Compliance is shown with an energy compliance form or software report in the permit set: COMcheck for commercial and REScheck for residential, both from the Department of Energy
• Inspections cover insulation, air sealing, windows, lighting controls, and in some jurisdictions blower door and commissioning
• Third-party testing (blower door, duct leakage, commissioning) is required in some provisions
• Appeals go to a board of appeals

How the code is organized

Using the code

The path through an energy code review:

1. Find the climate zone and the compliance path in IECC Envelope Insulation and Climate Zones
2. Set the assemblies and check air leakage in IECC Air Barrier Requirements
3. Select glazing and doors in IECC Fenestration U-Factor and SHGC
4. Design lighting and controls in IECC Commercial Lighting Power and Controls
5. Plan renewable, EV, and electrification readiness in IECC Renewable, EV, and Electrification Readiness
6. For existing buildings, apply the energy sections of the alteration and addition chapters in IEBC

Referenced standards

Sources

• NEEP: 2024 IECC resources and drafts, https://neep.org/sites/default/files/media-files/2024_iecc_commercial_11.29.23.pdf
• Data Driven AEC: IECC energy code requirements, https://datadrivenaec.com/insights/iecc-energy-code-requirements
• U.S. Department of Energy: Building Energy Codes Program, https://www.energycodes.gov/