Preparing Homebuilders for the 2024 International Energy Conservation Code (IECC) and Beyond

Building beyond the IECC energy code

By Gayathri Vijayakumar

Outside of California, states tend to adopt an iteration of the International Energy Conservation Code (IECC) as their residential code. Even though we are halfway through 2022, only a few states have adopted the 2021 IECC, with a few more considering it.

The PNNL Energy Savings analysis details significant changes to the insulation & air leakage test requirements, as well as introduces an ‘additional efficiency’ section, R408. However, the next iteration, the 2024 IECC is already under development, with hundreds of proposals received during the call for proposed changes back in October 2021.

This time, the IECC is being developed as a standard rather than a code, so the proposals move through the evaluation process a bit different than in years past. A diverse and balanced voting body of about 45 members hears each proposal and votes, often (but not always) following the recommendation of a Sub-Committee. There were about 200 proposals submitted, and they were mostly divided across 5 Sub-Committees (Envelope, HVAC, Existing Buildings, Modeling and Electrical & Renewables), also with diverse and balanced membership.

By July 2022, the Residential Consensus Committee will have heard and voted on all 200 proposals and the next step will be to combine all the approved proposals to produce the first rough draft of the 2024 IECC. Under the new process as a standard, this draft will be subject to public comment in the fall of 2022.

So, what can you do as a homebuilder to prepare for the 2024 IECC? I expect that nothing I am about to say will be news to you if you are already interested in building green: switch to heat pumps for space heat and hot water, replace gas cooking with induction, reduce your loads, think about the embodied carbon impacts of your design choices, add EV chargers, solar and batteries. However, only some of those are even proposed for 2024 IECC, while some are just incremental in nature.

While this first draft does not propose to ban fossil fuels and does not mandate solar PV or electric vehicle chargers in each new construction home, it does make some initial steps in that direction, which is part of the Committee’s charge: developing a glide path to zero by the 2030 IECC. 


While everything is subject to change, one proposal that had high levels of support was to expand the current R408 section to a points-based system that provides more options to achieve additional efficiency when choosing the prescriptive compliance path. The point system is structured to provide points that reflect the energy savings of certain measures in their respective climate zones. It then allows flexibility when choosing measures that achieve 10 points (roughly 10% energy savings).

While the Energy Rating Index (ERI) path was always intended to provide that flexibility, the max ERI values of the 2021 IECC resulted in values 48-52, which makes it an unpopular path given how much more efficiency that requires than the other paths. The first draft of the 2024 IECC updates this section significantly to ensure more parity with the other compliance paths. 

Rather than lowering the max ERI further, changes were approved that make it more aligned with a HERS Index in the low 50s and while a maximum CO2e Index was not introduced, this new metric will at least be reported such that future iterations might be able to set a CO2e Index threshold that allows us to focus both on energy savings, as well as greenhouse gas emissions.

If you have not yet electrified your buildings, an entire section devoted to electric-readiness mandates will be part of the first draft. This is not just limited to hot water and appliances, but also with respect to electric vehicles. 

Other incremental changes include lowering the envelope air leakage thresholds, expanding the ERV/HRV requirement beyond just Climate Zones seven and eight, and improvements to the chapter for existing buildings and the optional net zero Appendix. Notably missing are changes that would encourage or mandate that builders choose products with lower embodied carbon.

Again, it feels like I may be preaching to the choir here and most of you know what to do and are already on your own glide path to zero. So I’ll end with a request rather than any other recommendations on how to get prepared: participate in the public comment period. Join a Sub-Committee. Attend the meetings. Provide supportive public comments on changes that you think will get us closer to zero, sooner.  During the debates this past Spring, the testimony that was missing was the one of the builders already building green and doing it successfully and cost-effectively. It’s not too late for your voice and experience to help shape the 2024 IECC.

Gayathri Vijayakumar is a Principal Mechanical Engineer at Steven Winter Associates, a mission-driven high-performance building consulting firm. She can be reached at