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The 2024 International Energy Conservation Code (IECC) has undergone over two years of development and is nearing its final stages prior to publication. The Residential IECC Committee meticulously reviewed approximately 500 proposals and public comments across 40 committee meetings and numerous subcommittee sessions. The endorsed proposals have led to numerous enhancements, anticipating substantial energy savings, providing builders and designers with greater flexibility to construct more energy-efficient homes.

The IECC and its predecessor, the Model Energy Code (MEC), have shown a consistent increase in residential home efficiency over the last four decades. The U.S. Department of Energy (DOE) has been monitoring efficiency improvements in energy codes since the publication of the ASHRAE 90 Efficiency Standard in 1975. The improvement in energy savings, especially since 2006, has been dramatic and is illustrated in the figure below:

For the 2024 edition, a new code development process was introduced, transitioning from the International Code Council’s (ICC) Governmental Consensus Process to a committee development process. This change aims to facilitate increased deliberations with a balanced committee representing various stakeholders in the construction industry.

Photo credit: JELD-WEN

Noteworthy changes in the 2024 IECC, compared to the 2021 IECC, include:

  • Windows and Doors: A 7 to 10% increase in efficiency in northern climate zones.
  • Skylights: A 5 to 20% increase in efficiency across all climate zones.
  • Air Tightness: Homes must be approximately 20% tighter when tested using a pressurization test.
  • Attic Insulation: A 20-25% reduction in efficiency (addressed cost-effectiveness concerns).
  • Air Sealing, Insulation Installation Requirements: Updated requirements for sealing around windows, doors, fireplaces and common walls.
  • Electric Vehicle (EV) Charging: Single-family homes with parking must have a 40 Amp 240 V receptacle nearby. (Moved to an adoptable appendix based on a successful appeal)
  • Solar Ready: All single-family homes must have roofs designed to be “solar ready,” including roof space allocation, a conduit from the attic to the electric panel, and sufficient panel space. (Moved to an adoptable appendix based on a successful appeal)
  • Electric Ready: Gas water heaters, dryers, and stoves must have electric wiring back to the electric panel suitable for potential electric replacements. (Moved to an adoptable appendix based on a successful appeal)
  • Efficiency Credits: Additional efficiency credits have been added beyond the typical prescriptive requirements. These new credits equate to approximately a 5% increase in efficiency.
  • Equipment Trade-Off: Limited trade-offs have been reinstated for heating and cooling equipment with efficiencies above the Federal minimum against other requirements for code compliance.
  • Adoptable Appendices: New appendices were added that can be adopted by a jurisdiction including- Electric Energy Storage Provisions, All-Electric Residential Buildings, Alternative Building Thermal Envelope R-values.

The Pacific Northwest National Laboratory (PNNL) has conducted analyses, including an interim one, comparing energy savings between the First Draft of the 2024 IECC and the 2021 IECC. Energy cost savings were determined to be 7.7% (this does not represent the savings associated with the approved version, but likely similar).

Photo credit: VELUX

The 2024 International Energy Conservation Code (IECC) and the 2024 International Residential Code (IRC) are now approved by the board with no further appeals and is expected to be published in April 2024.

Photo credit: ProVia

Written by Craig Drumheller.

Craig Drumheller is the Vice President of Technical Activities with the Window & Door Manufacturers Association. He has been involved in energy efficiency research and energy code development for over 20 years. Craig has been a member of ASHRAE Standards 90.1, 90.2, and the IECC residential energy code development committee.

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