Austin Energy Code Multifamily: 2024 IECC, ASHRAE 90.1-2022, and When to Study First

If you are building multifamily inside the City of Austin, a statewide Texas summary or a Houston summary is the wrong filing target. Austin adopted the 2024 International Energy Conservation Code with local amendments, effective July 10, 2025, and pairs the commercial ASHRAE path with ASHRAE 90.1-2022, not the 2021 IECC / 90.1-2019 stack Houston enforces. Teams get caught when they model to the 2015 state floor, copy a Houston COMcheck package into an Austin submittal, or discover solar-ready, EV-ready, electric-ready, and demand-response appendices only after the drawings are frozen.

This page is the Austin Energy Code door for multifamily developers. For the statewide Texas commercial code path (the 2015 IECC floor, ASHRAE pairings, and why mid-rise is not HERS-first), see ASHRAE COMcheck Texas multifamily. For the Texas study door, see energy code feasibility study Texas. For the other Texas city door already live, see Houston Energy Code multifamily. City-code doors in other ECC priority markets: NYC Energy Code multifamily. Program and modeling context: ENERGY STAR Multifamily New Construction and multifamily energy modeling.

What Code Applies in Austin Right Now

Per the City of Austin Building Technical Codes page, Council backup File 25-0396 / EDIMS document 447381 (the ordinance adopting the 2024 IECC), and Austin Energy Green Building's policies and code page (primary sources; confirm with the City before you file):

• The City repealed and replaced City Code Chapter 25-12, Article 12 (Energy Code) to adopt the 2024 International Energy Conservation Code, including Appendices CG, CH, CI, CJ, RE, RF, RJ, and RK, with local deletions and amendments.
• Local amendments for the IECC (and the rest of the 2024 technical codes) are listed as effective July 10, 2025.
• Austin Energy Green Building states the City updated its Energy Code to the 2024 IECC with local amendments, with changes effective July 10, 2025, and published commercial renewable energy and EV readiness guides for the new requirements.
• For commercial energy efficiency compliance with ASHRAE standards as allowed under the 2024 IECC, Austin adopts ASHRAE 90.1-2022 with listed deletions and local amendments (not ASHRAE 90.1-2019).
• The residential design-condition table in the local amendments places Austin in climate zone 2A.

Houston, by contrast, still enforces the 2021 IECC and ASHRAE 90.1-2019 with Houston amendments (effective January 1, 2024). Statewide Texas still sits on a 2015 IECC floor for many jurisdictions. Austin is on a newer stack. Code lists change. Use the City of Austin Development Services and Austin Energy pages as the source of truth for your filing date, not a blog summary.

Residential vs Commercial Split for Multifamily

Austin's local amendments keep a height-based residential definition that matters for multifamily:

• Residential Building (Austin amendment to R202 / R101.2). Detached one- and two-family dwellings and townhouses, plus Group R-2, R-3, and R-4 buildings four stories or less above grade plane, sit on the residential provisions of the 2024 IECC as amended.
• Taller residential and most mixed-use. Once you leave that residential definition, you are on the commercial provisions of the 2024 IECC or the ASHRAE 90.1-2022 option, with Austin's commercial deletions and additions.
• Podium and mixed-use projects. Retail, amenity, lobby, corridor, parking, and other non-dwelling areas follow commercial documentation even when the team thinks of the job as "apartments."

That split decides whether you are looking at residential envelope tables, ERI or other residential paths, or a commercial / ASHRAE package with COMcheck-style certificates and performance modeling. Guessing it after glazing, wall assemblies, and HVAC are bought is an expensive rewrite. Confirm it with Austin plan review before anyone models.

The ASHRAE 90.1-2022 Commercial Path

Under the adopting ordinance, commercial projects that use the ASHRAE path allowed by the 2024 IECC use ASHRAE 90.1-2022, with specific sections deleted and replaced by Austin amendments. At a high level (not a design checklist):

• Austin writes commercial solar-ready, cool-roof, insulation encapsulation, demand-responsive controls, additional electric infrastructure for combustion equipment, on-site renewable capacity, electrical energy storage readiness, and EV power-transfer infrastructure into the Energy Code path.
• On-site renewable and EV requirements sit alongside the base ASHRAE or IECC commercial compliance method. Which thresholds and exceptions apply depends on roof geometry, downtown network location, hazard classification, parking count, and occupancy group.
• Austin Energy Green Building publishes separate commercial renewable energy and EV readiness guides for the 2024 IECC changes. Use those City / AEGB guides and the adopted text for the numbers that bind your building.

This is not Houston's 90.1-2019 stack and not the statewide 2015 floor. Lock the edition year before you buy modeling hours.

Adopted Appendices (High Level)

Ordinance File 25-0396 adopts Appendices CG, CH, CI, CJ on the commercial side and RE, RF, RJ, RK on the residential side, with local deletions. In plain language, those appendices cover topics teams often miss until late design:

• EV readiness (for example CG / related ASHRAE EV sections). Parking facilities need EV capable, EV ready, and related infrastructure counts by occupancy, with alternate power-allocation methods and long-term parking garage rules. AEGB publishes multifamily and commercial EV readiness guides for the July 10, 2025 effective date.
• Electric-ready / additional electric infrastructure (for example CH and related ASHRAE sections). Spaces with combustion equipment for space heating, water heating, cooking, or drying may need spare branch circuits, labeled panels, chase space, or designated exterior locations sized for future electric equipment. Some multifamily central water-heating exceptions appear in the adopted text.
• Renewables and solar-ready. Commercial solar-ready zones, reserved electrical capacity "For Future Solar Electric," and on-site renewable capacity criteria appear in the local amendments and AEGB's commercial renewable energy guide.
• Demand response (for example CI). Electric heating and cooling systems, and certain electric storage water heaters, need demand-responsive controls capable of setpoint shifts or heater response, with listed occupancy and application exceptions.

Treat those as path facts, not as invented amp, kVA, or panel specs. The adopted tables and AEGB guides are the numbers to design against. Which appendices bind your building depends on residential vs commercial classification, parking, fuel mix, and the compliance method.

Proof From ECC Studies (Method, Not Austin Invoices)

ECC does not publish an Austin or Texas dollar-per-square-foot average, and we do not have an Austin energy-code invoice to present as your number. We cite other studies as proof of method, and we label them that way.

On our 267-unit Cromwell, CT study (CS68), two buildings up to six stories (272,036 square feet) were filed on IECC commercial provisions using ASHRAE 90.1-2019 Appendix G. The recommended all-electric tier came in at about $35.23 per square foot net and captured a $1,500 per unit Energize CT incentive ($400,500). Those are Connecticut commercial-code outcomes, not Austin invoices. They show the order: lock the ASHRAE path and edition year, rank the packages, then document the winner.

On a 112-unit Revere, MA study (CS57), a seven-story mixed-use building kept dwelling units on a Massachusetts Stretch HERS path and still called for a COMcheck report for all common and support areas, plus ASHRAE 62.1 ventilation calculations and lighting power density calculations. The recommended ductless package landed at about $42.52 per square foot net. Those are Massachusetts outcomes. We cite them as proof that mixed-use paperwork splits before modeling hours, not as an Austin price.

Common Mistakes on Austin Multifamily Energy Filings

• Modeling to the statewide floor. Austin enforces the 2024 IECC with local amendments and ASHRAE 90.1-2022 on the commercial ASHRAE path, not the 2015 state minimum.
• Copying a Houston package. Houston is still on 2021 IECC / ASHRAE 90.1-2019. Austin's edition year, appendices, and AEGB guides are different.
• Missing the residential height definition. Austin's amended residential scope includes Group R-2 / R-3 / R-4 four stories or less above grade. Taller residential and mixed-use non-dwelling areas follow commercial or ASHRAE documentation.
• Ignoring solar-ready, renewables, EV, electric-ready, and demand-response appendices until CD. Those scopes affect parking, electrical rooms, roof layout, and mechanical rooms. Late discovery means redraws.
• Buying HERS or COMcheck hours before the path is locked. The study should settle residential vs commercial, IECC vs ASHRAE 90.1-2022, and which appendices apply, then the paperwork follows.

When to Study First

Settle the Austin path before anyone buys REScheck, COMcheck, ERI, or whole-building modeling hours:

1. Confirm the permit address is inside the City of Austin and on the Energy Code effective for your filing date (2024 IECC amendments in force since July 10, 2025)
2. Lock the residential vs commercial split using Austin's amended residential definition (four stories or less for Group R-2 / R-3 / R-4) and commercial documentation for nonresidential areas
3. Pick the compliance method for each portion: residential provisions, commercial IECC, or ASHRAE 90.1-2022
4. Flag which adopted appendices apply (EV, electric-ready, renewables / solar-ready, demand response) and pull the matching AEGB guides
5. Model envelope and HVAC packages side by side against that method, including ENERGY STAR Multifamily New Construction where you plan to enroll
6. Then produce the certificates, reports, and checklists against the locked plan

That comparison is what a free feasibility study produces. For the Texas study method, see energy code feasibility study Texas. For how modeling works on apartment buildings in general, see multifamily energy modeling. If the path is already chosen and you need COMchecks, modeling, inspections, or testing, see ECC services.

Bottom Line

The Austin energy code for multifamily is the 2024 IECC with Austin amendments, effective July 10, 2025, with ASHRAE 90.1-2022 on the commercial ASHRAE path and adopted appendices for EV readiness, electric-ready infrastructure, renewables, and demand response. That is a newer stack than Houston's 2021 IECC / 90.1-2019 and a higher bar than the statewide 2015 IECC floor. This is the Austin city-code door, not the statewide Texas code-path page, not the Houston city door, and not the Texas study door. Lock the split, the edition year, and the appendices first, then buy the paperwork that matches the plan.