2024 IECC Offers More Energy Savings and Lower Building Costs, Per Studies
The 2024 International Energy Conservation Code (IECC) offers home builders more compliance paths and lower building costs compared to the 2021 IECC, according to a cost analysis by Home Innovation Research Labs.
The Department of Energy (DOE) had previously issued a determination on the 2024 IECC showing that it will provide a 6.6% energy cost savings over the 2021 IECC, meaning the 2024 version is also better for energy conservation.
NAHB staff and members served on the 2024 IECC Residential consensus committee to ensure that builder’s interests were well represented, and affordable homeownership was at the forefront of committee deliberations. The 2024 IECC provides for increased design flexibility and improved compliance options.
Following DOE’s determination, some states may start reviewing the 2024 IECC and consider adoption. NAHB developed a code adoption kit for home builder associations (HBAs) in states evaluating the 2024 IECC. The kit includes recommended amendments, a cost analysis of code changes and other resources.
The cost analysis from Home Innovation shows significant cost savings for the 2024 IECC compared to the 2021 IECC in many, but not all, climate zones. See the table below from the Home Innovation report for a comparison between the 2024 and 2021 editions of the IECC. For cases where a jurisdiction would be transitioning directly from the 2018 IECC (or an earlier edition) to the 2024 IECC, an incremental increase in first cost will be expected in all climate zones.
Added Cost of 2024 IECC Relative to 2021 IECC by Climate Zone (CZ)
| CZ 2 | CZ 3 | CZ 4A/B | CZ 4C | CZ 5 | CZ 6 | CZ 7 | ||||
| Configuration* | Slab | Slab | Crawl | Crawl | Bsmnt | Crawl | Slab | Bsmnt | Bsmnt | Bsmnt |
| Gas, HVAC | $1,176 | $277 | $277 | ($4,402) | ($4,256) | ($5,779) | ($3,928) | ($3,770) | $4,025 | $2,018 |
| Gas, WH | $1,052 | $154 | $154 | ($4,526) | ($4,380) | ($5,666) | ($3,815) | ($3,657) | $4,137 | $2,131 |
| Electric, HVAC | ($440) | ($1,338) | ($1,338) | ($6,850) | ($6,704) | ($7,560) | ($6,759) | ($6,602) | $2,155 | $148 |
| Electric, WH | $64 | ($835) | ($835) | ($6,609) | ($6,462) | ($2,065) | ($1,264) | ($1,106) | $7,650 | $5,643 |
| *Cost comparison based on 2021 IECC R408 option used for compliance: HVAC or Water Heater (WH) For a map of climate zones, see the General Requirements of the IECC. NOTE: Red ink denotes a cost savings in the 2024 IECC. |
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The 2024 IECC includes many significant changes across the prescriptive, performance, and energy rating index (ERI) compliance paths. One of the significant changes is the expansion of Section R408 Additional Efficiency Requirements. R408 sets up a system of optional measures with credits based on efficiency and climate zone with a requirement to achieve a minimum of 10 credits from at least two measures. R408 includes a list of more than 50 measures from which builders and designers can chose. Building designers will need to identify the most cost-effective method for compliance with R408 for their projects and will have to ensure coordination between framing, insulation, plumbing and HVAC subcontractors.
Examples of R408 Compliance (in addition to meeting all other prescriptive requirements) based on the 2024 IECC climate zone map:
Climate Zone 2
- High performance heat pump with electric resistance – 7.8 HSPF2 and 15.2 SEER2 – 12 credits
- Demand responsive thermostat – 1 credit
Climate Zone 4
- High performance gas furnace and cooling – 95 AFUE and 15.2 SEER2 – 5 credits
- Gas-fried instantaneous water heater – 0.92 UEF – credits
Climate Zone 5
- 80% of ductwork in conditioned space – 7 credits
- High performance gas furnace – 95 AFUE – 5 credits
Visit the NAHB 2024 IECC Code Adoption Tool Kit for more information on the latest model energy code. Most state and local jurisdictions amend model codes, to a varying degree, at the adoption stage – this is an integral step in the code development process. It is important that jurisdictions perform their due diligence in evaluating the impact of new changes on local construction practices and implement amendments that address local conditions. For additional assistance around local adoption of energy codes, please reach out to Paul Karrer or Nathan Kahre.