Denton TX Energy Code Multifamily: 2021 IECC, Local Amendments, and When to Study First

If you are building multifamily inside the City of Denton, Texas, you are on the 2021 International Energy Conservation Code, not the 2024 edition several nearby cities have moved to. Denton adopted the 2021 IECC with local deletions and amendments by Ordinance 22-661, which repealed the 2015 IECC and took effect June 1, 2022. The City's permit pages still state that permits applied for on or after June 1, 2022 must meet the 2021 International Codes. That puts Denton with Dallas, Arlington, Houston, San Antonio, and El Paso on the 2021 IECC, while Frisco, Plano, McKinney, and Austin are on the 2024 IECC. Teams get caught when they carry a Frisco or McKinney 2024 package over to Denton, or when they skip the R-2 testing sample Denton wrote into its amendments.

This page is the Denton 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. Other Texas city doors already live: Houston Energy Code multifamily, Austin Energy Code multifamily, Dallas Energy Code multifamily, San Antonio Energy Code multifamily, Fort Worth Energy Code multifamily, El Paso Energy Code multifamily, Corpus Christi Energy Code multifamily, Arlington Energy Code multifamily, Plano Energy Code multifamily, McKinney Energy Code multifamily, and Frisco Energy Code multifamily. Program, testing, and modeling context: ENERGY STAR Multifamily New Construction, blower door testing for multifamily buildings, and multifamily energy modeling.

What Code Applies in Denton Right Now

Per the City of Denton Residential Permits page and the City's adopted ordinance (primary sources; confirm with the City before you file):

• The City states that it has adopted the 2021 International Building Codes and that all permits applied for on or after June 1, 2022 must meet them. The City's 2021 adoption list includes the 2021 IBC, IEBC, IRC, IMC, IPC, IFGC, IECC, ISPSC, and IFC, plus the 2020 NEC, each with local amendments.
• Ordinance 22-661 repealed the 2015 IECC in former Sections 28-253 and 28-254 and adopted the 2021 IECC in new Sections 28-85 and 28-86 of Chapter 28 of the Denton Code of Ordinances, with the deletions and amendments listed in Section 28-86. It was recommended by the Health and Building Standards Commission at its March 24, 2022 meeting and took effect June 1, 2022.
• In 2025, City staff reported on updating the building codes so new single-family homes would be EV-ready and solar-ready through code appendices. At its July 22, 2025 work session, City Council's direction was to take no action on that code change. That direction left the 2021 codes in place without a new EV-ready or solar-ready mandate.

Denton sits in Denton County, climate zone 3A (warm, humid), the same zone as Frisco, Plano, McKinney, Dallas, Fort Worth, and Arlington. Same zone as Frisco, but a different edition. Do not copy a 2024 IECC package from the next city over.

What Denton Changed in the 2021 IECC

The Denton amendments in Section 28-86 that matter most for apartment projects:

• Alternative compliance (C102.1.2 and R102.1.2). A building certified by a national, state, or local accredited energy efficiency program and determined by the Energy Systems Laboratory to comply may, at the Code Official's option, be considered in compliance. ENERGY STAR certification of energy code equivalency is considered in compliance. On the residential side, each 1- and 2-family dwelling is still tested for air and duct leakage regardless of program or path.
• Dwelling and sleeping unit enclosure testing (C402.5.2). Under the commercial provisions, the building thermal envelope is tested to ASTM E779, ANSI/RESNET/ICC 380, ASTM E1827, or an approved equivalent, with measured air leakage no more than 0.30 cfm per square foot of testing unit enclosure area at 50 Pa. Each dwelling unit is its own testing unit, results are weighted by enclosure area, and units are tested separately with an unguarded blower door.
• R-2 sampling on the residential provisions (R402.4.1.4, R403.3.8, R403.6.4). For buildings with eight or more testing units, the greater of seven units or 20 percent of the units are tested for air leakage, duct leakage, and ventilation, including a top floor unit, a ground floor unit, a middle floor unit, and the largest unit. Each failing unit adds three more tests. Buildings with fewer than eight units test every unit. The same sample rules apply to commercial enclosure testing.
• Performance path replaced (R405.2). A proposed design must meet the mandatory sections in Table R405.2, keep the thermal envelope at or above the 2009 IECC levels, and show an annual energy cost at or below the 2021 standard reference design, or 8 percent below the 2018 standard reference design. Source energy may be substituted for cost, with an electricity multiplier of 3.16.
• Residential extras removed. R401.2.5 additional energy efficiency and R408 additional efficiency package options are deleted, R404.2 interior lighting controls is deleted, and the ERI table R406.5 is replaced with a schedule that steps on September 1, 2022, September 1, 2025, and September 1, 2028.
• Other local changes. Air-sealed outlet boxes (R402.4.6) are replaced with a requirement that boxes in the thermal envelope be sealed against air leakage, the prescriptive U-factor and R-value tables (R402.1.2 and R402.1.3) are replaced with Denton versions, and appeals go to the City's Health and Building Standards Commission.

Residential vs Commercial Split for Multifamily

The 2021 IECC draws the line by building type and height. Group R-2, R-3, and R-4 buildings three stories or less above grade plane fall under the residential provisions. Taller apartment buildings, and the nonresidential portions of any building, fall under the commercial provisions, where the 2021 IECC commercial chapter or its ASHRAE 90.1-2019 alternative applies.

• Mid-rise, podium, and mixed-use projects. Retail, amenity, lobby, corridor, and parking areas follow commercial documentation, and dwelling units still face Denton's enclosure testing limit and sample. Price the blower door program with the envelope, not after it.
• Garden-style and townhome projects. Three stories or less usually lands on the residential provisions, where the R-2 sampling rules for air, duct, and ventilation testing set how many units get tested and what a failure costs in retests.

Proof From ECC Studies (Method, Not Denton Invoices)

ECC does not publish a Denton or Texas dollar-per-square-foot average, and we do not have a Denton 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 same ASHRAE year that pairs with Denton's 2021 IECC. 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 outcomes, not Denton invoices. They show the order: lock the path and edition, 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 a Denton price.

Common Mistakes on Denton Multifamily Energy Filings

• Pricing a 2024 IECC package. Frisco, Plano, and McKinney are on the 2024 IECC. Denton is still on the 2021 IECC under Ordinance 22-661.
• Pairing the wrong ASHRAE year. The 2021 IECC commercial alternative is ASHRAE 90.1-2019, not 90.1-2022.
• Testing too few units. Eight or more units means the greater of seven units or 20 percent, with a top, ground, middle, and largest unit in the sample, and three more tests for every failure.
• Planning on R408 efficiency packages. Denton deleted the additional efficiency package options and the R401.2.5 requirement that points to them.
• Running the performance path against the model text. Denton's R405.2 sets its own cost test (2021 reference, or 8 percent better than the 2018 reference) and a 2009 IECC envelope backstop.
• Buying REScheck, COMcheck, or ERI hours before the path is locked. The study should settle residential vs commercial, 2021 IECC vs ASHRAE 90.1-2019 for commercial areas, the alternative compliance option, and the testing sample, then the paperwork follows.

When to Study First

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

1. Confirm the permit address is inside the City of Denton and on the 2021 IECC as amended by Ordinance 22-661 for your filing date
2. Lock the residential vs commercial split (three stories or less for Group R-2 / R-3 / R-4 on the residential provisions, and commercial documentation for nonresidential areas)
3. For each commercial portion, pick 2021 IECC commercial or ASHRAE 90.1-2019
4. Decide whether an accredited program path, such as ENERGY STAR Multifamily New Construction, is worth using for alternative compliance
5. Model envelope, window, ventilation, and HVAC packages side by side for climate zone 3A, and size the air, duct, and ventilation testing sample early
6. Produce the COMcheck reports, performance models, and test results 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 Denton energy code for multifamily is the 2021 IECC with the City's own amendments in Section 28-86, adopted by Ordinance 22-661 and effective June 1, 2022. Denton kept alternative compliance through accredited programs and ENERGY STAR equivalency, wrote R-2 sampling into air, duct, and ventilation testing, set a 0.30 cfm per square foot enclosure limit for dwelling units on the commercial side, and replaced the residential performance path, all in climate zone 3A. This is the Denton city-code door, not the statewide Texas code-path page, not the Houston, Austin, Dallas, San Antonio, Fort Worth, El Paso, Corpus Christi, Arlington, Plano, McKinney, or Frisco city doors, and not the Texas study door. Lock the split, the edition, and the testing sample first, then buy the paperwork that matches the plan.