Texas Energy Code Amendments and Multifamily MEP Design: A City-by-City Guide

Texas has a statewide energy code, but no developer builds in "Texas." You build in a city, and that city decides which edition of the energy code applies and how it has been amended. A four-story apartment building can be designed under three different IECC editions depending on whether it sits in Plano, Dallas, or Fort Worth.

For multifamily owners and architects working in more than one market, those differences show up in the mechanical, electrical, and plumbing design, not just on the code summary sheet.

The Statewide Floor

For buildings other than single-family homes, the State Energy Conservation Office (SECO) continues to use the 2015 IECC as the statewide energy code, in effect since November 1, 2016. Cities may adopt newer editions and local amendments. In nonattainment and affected counties, which include the major metros, local amendments may not make energy-efficiency requirements less stringent, and the Energy Systems Laboratory at Texas A&M evaluates proposed amendments on request.

Most of the large cities we work in have moved well past the state minimum. As of this writing:

City	Energy code in effect	Effective
Dallas	2021 IECC with Dallas amendments	May 12, 2023
Fort Worth	2015 IECC with local amendments (2013 ASHRAE 90.1 allowed as an alternative)	Retained when the 2021 codes took effect April 1, 2022
Plano	2024 IECC with Plano amendments	August 1, 2025
Houston	2021 IECC and ASHRAE 90.1-2019, both with Houston amendments	January 1, 2024
Austin	2024 IECC with local amendments	July 10, 2025
San Antonio	2021 IECC with local amendments	February 1, 2023

San Antonio moved its building, mechanical, plumbing, and fire codes to the 2024 editions effective May 1, 2025, but kept the 2021 IECC. Fort Worth did the same thing a cycle earlier, adopting the 2021 building codes while keeping the 2015 IECC.

First Question: Residential or Commercial Provisions?

Under the model IECC, Group R-2 apartment buildings three stories or less above grade plane follow the residential provisions, and those four stories or more follow the commercial provisions. We covered why that split matters in our post on energy recovery ventilators in multifamily.

Austin moves the line. Its amended residential scope covers Group R-2, R-3, and R-4 buildings four stories or less above grade plane. A four-story wrap project that falls under the commercial provisions in Dallas or Houston falls under the residential provisions in Austin. Envelope tables, testing, ventilation, and the compliance software all change with it.

Climate zone is the second variable. Starting with the 2021 IECC, Dallas and Tarrant counties moved from Climate Zone 3A to 2A. Collin County, where most of Plano sits, remains 3A, and Harris, Travis, and Bexar counties are 2A. Because Fort Worth still enforces the 2015 IECC, a Fort Worth project is evaluated under that edition's climate zone map, not the newer one. Table C301.1 of the 2015 IECC lists Tarrant County as Climate Zone 3A. Climate zone affects envelope requirements and several mechanical exceptions, including the energy recovery exceptions for small dwelling units.

What the Local Amendments Change for MEP

Dallas

Dallas amends the commercial dwelling-unit air leakage test (C402.5.2) to a maximum of 0.30 cfm per square foot of enclosure area at 50 Pa, with sampling: the greater of seven units or 20 percent of units, including a top-floor, ground-floor, middle-floor, and largest unit. Each failing unit adds three more tests. Similar sampling rules apply to residential-code air leakage, duct leakage, and ventilation testing.

The design point is simple: ventilation rates, duct leakage, and exhaust paths are verified in the field, so the drawings need to make those results achievable. Dallas also requires a commercial energy compliance path form with the permit application.

Fort Worth

Fort Worth projects choose either the 2015 IECC or ASHRAE 90.1-2013 and must use that standard in its entirety. The dwelling-unit energy recovery provision now found in C403.7.4.1 of the newer IECC editions is not part of the 2015 IECC, and Fort Worth's local amendments do not add a comparable dwelling-unit ERV requirement, so the ERV analysis for a mid-rise project in Fort Worth is different from the same building in Dallas.

Plano

Plano's 2024 IECC amendments rewrite the commercial ERV section for nontransient dwelling units. In addition to the model enthalpy recovery ratio option, Plano allows a sensible recovery efficiency of at least 65 percent at 32°F with a net moisture transfer of at least 40 percent at 95°F in Climate Zones 0A through 3A, and adds an exception for dwelling units using ventilation systems per the fan efficacy table in R406. Plano also deleted the residential R408 additional efficiency requirements and the commercial dwelling-unit lighting and switched receptacle control section. How Plano applies the R406 fan-efficacy exception on a given project should be confirmed with the city and the engineer of record.

Houston

Houston adopted the same R-2 sampling approach for residential-code air leakage, duct leakage, and ventilation testing. On the commercial side, total building performance reports must be sealed by a Texas-licensed professional engineer, and Houston fixes the exterior design conditions used in the performance path. Houston also adopted the optional solar-ready and EV-ready appendices; for R-2 buildings, EV infrastructure is based on the lesser of dwelling units or parking spaces.

Austin

Beyond the four-story residential scope, Austin's 2024 IECC adoption includes appendices for EV readiness, electric-ready buildings, demand-responsive controls, and energy storage readiness. For R-2 parking, Austin's table calls for 5 percent EV-ready and 35 percent EV-capable spaces. The electric-ready provisions require labeled spare circuits near certain gas appliances, with an exception for water heaters serving multiple R-2 dwelling units. Commercial-code buildings also carry an on-site renewable energy requirement. Under Austin's adopted C405.15.1, the on-site system must have a DC nameplate rating of at least 0.75 watts per square foot, multiplied by the gross conditioned floor area of all floors, not to exceed the combined area of the three largest floors. Several exceptions, including buildings under 5,000 square feet and sites with limited solar area, allow off-site renewable procurement instead. Confirm the current exceptions with the city before schematic design.

San Antonio

San Antonio requires a separate electrical meter for each dwelling unit in an R-2 building. It adds an EV-capable section requiring service and panel capacity for 5 percent of required parking, at one future 40-amp breaker per two spaces, labeled "For Future EV." Hot water recirculation pumps need demand-based controls or a timer with a return-temperature switch, and the energy monitoring threshold rises to 100,000 square feet.

What This Means on Your Next Project

• Confirm the code by city and permit date. Code editions turn over every few years, and the application date usually controls.
• Classify the building before schematic design. Story count, occupancy, and the city's residential scope decide which provisions apply.
• Pick the compliance path early. Prescriptive versus performance affects ERVs, glazing, and equipment efficiencies. Our Energy & Sustainability team runs that comparison while it can still change the design.
• Design for the test. Where cities require unit-by-unit testing, mechanical layouts, duct sealing, and ventilation controls should be selected with the test in mind.
• Size the electrical service for local readiness rules. EV-capable spaces, separate meters, and spare circuits all add load and panel space.
• Do not copy a spec from one city to the next. A building that complies in Dallas may not comply in Austin, and the reverse is true too.

The takeaway: In Texas, the energy code is local. Before the first mechanical layout, confirm the city's adopted edition, its amendments, how it classifies the building, and the climate zone. Those four answers drive a large share of the multifamily MEP design.

Talk with V3 about energy code compliance on your next multifamily project.

This article summarizes adopted codes and amendments as of its publication date. Requirements change with new adoptions, and it is not a substitute for a project-specific code analysis.