Houston Energy Code Multifamily: 2021 IECC, COMcheck Rules, and When to Study First

If you are building multifamily inside the City of Houston, the statewide Texas summary is not your filing target. Houston adopts and amends its own construction code, and its energy code is the 2021 IECC and ASHRAE 90.1-2019 with Houston amendments. The building height decides which chapter you file under, and Houston plan review rejects an incomplete COMcheck at prescreen. Teams get caught when they model to the 2015 state floor, assume a four-story apartment building is a residential filing, or upload a COMcheck with the default "requirement will be met" comments still in it.

This page is the Houston 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. City-code doors in other ECC priority markets: NYC Energy Code multifamily. Commercial-paperwork doors in other states: COMcheck Florida multifamily and COMcheck Massachusetts mixed-use multifamily.

What Code Applies in Houston Right Now

Per the Houston Permitting Center (City of Houston Building Code Enforcement) current-codes list, Form CE-1199, and the Houston Code Archive (primary sources; confirm with the City before you file):

• The 2021 Houston Construction Code was approved by City Council on October 25, 2023 (Ordinance No. 2023-907) and took effect January 1, 2024.
• 2021 IECC with Houston amendments applies to one- and two-family dwellings and multifamily 3 stories or less (the City of Houston Residential Energy Conservation Code).
• 2021 IECC with Houston amendments applies to commercial structures, including residential structures more than 3 stories (the City of Houston Commercial Energy Conservation Code).
• ASHRAE 90.1-2019 with Houston amendments is also in force for commercial structures, including residential structures more than 3 stories.
• The City's design-condition table puts Houston in climate zone 2A.

The City's own notes on that list also record that enforcement of the IECC commercial provisions became mandatory by state law effective November 1, 2016. Houston is above the statewide 2015 IECC floor described on the Texas code-path page. Code lists change. Use the Houston Permitting Center pages as the source of truth for your filing date, not a blog summary.

The 3-Story Split Decides Your Filing

Houston writes the split into its code list: multifamily 3 stories or less sits on the residential provisions, and residential structures more than 3 stories sit on the commercial provisions or ASHRAE 90.1-2019. That one line decides what the energy package looks like:

• Garden and low-rise multifamily (3 stories or less). The residential chapter. For residential permits the City says plans must show prescriptive compliance with the 2021 IECC or include a REScheck, IC3, or REM/Rate compliance report. The Houston amendments also keep the Energy Rating Index (ERI) alternative, with R-2 sampling rules described below.
• Four stories and up, and most mixed-use. The commercial chapter or ASHRAE 90.1-2019. That is a COMcheck (or a total building performance model) problem, not a dwelling-unit HERS problem.
• Podium and mixed-use projects. Retail, amenity, lobby, corridor, and garage areas follow commercial documentation even when the team is used to thinking of the job as "apartments."

Guessing that split after glazing, wall assemblies, and HVAC are bought is an expensive rewrite. Confirm it with Houston plan review before anyone models.

Houston COMcheck Rules That Trip Teams Up

Per the City's COMcheck enforcement notice and its COMcheck Guideline (Form CE-1375, revised February 2024):

• A COMcheck report has been required on all commercial plan reviews since 2016. Since April 15, 2021, plans with incomplete COMcheck reports are rejected at prescreen.
• COMcheck must show compliance with either the 2021 IECC or ASHRAE 90.1-2019, and it is uploaded to the "Energy Forms - Codes" folder in ProjectDox.
• A full report has five parts: envelope, interior lighting, exterior lighting, and mechanical compliance certificates, plus the inspection checklist, which is required. Some alteration scopes may not need all four certificates.
• Every certificate needs the project, site, owner/agent, and designer/contractor fields completed, and the same additional efficiency package on each one. Envelope certificates need fenestration product ID numbers (or defaults) that match the plans.
• Each compliance statement is signed with name, title, and date. Licensed professionals affix their seal or license number.
• On the inspection checklist, COMcheck's default comments such as "Requirement will be met" or "Requirement does not apply" are not acceptable by themselves. The comment has to point the reviewer to the sheet, note, or detail that shows compliance, or name the specific code exception.
• Mechanical compliance also needs ASHRAE Standard 183 load calculations, refrigeration manufacturer data where it applies, and, unless an exemption is claimed, the commissioning submittal form (CE-1190) filed with the COMcheck.
• Resubmittals mean reprinting the entire report from COMcheck. Digitally edited printouts of a rejected report are not accepted.

Where can I get a COMcheck for Houston? The software is free from DOE. A report that clears Houston prescreen is built from your drawings, cross-referenced sheet by sheet, and signed by someone who will stand behind the inputs. ECC prepares COMcheck and related commercial documentation as permit paperwork once the path is locked. If it already is, see ECC services.

Performance Path and ERI Details in the Houston Amendments

The Houston amendments to the 2021 IECC (Ordinance No. 2023-907) change a few things teams carry over from other cities:

• Commercial total building performance (C407). The permit compliance report must include the building address, an inspection checklist showing estimated annual energy cost for the standard reference design and the proposed design, the name of the person completing it, the software name and version, and the seal, signature, and date of a Professional Engineer licensed in Texas.
• Residential ERI (R406). Houston's maximum ERI for climate zone 2 is 57 for permits from September 1, 2025 through August 31, 2028, then 55 from September 1, 2028 to September 1, 2031 (it was 59 before September 1, 2025).
• R-2 multifamily testing samples. For buildings with eight or more testing units, the greater of seven units or 20 percent of the testing units are tested for air leakage, including a top floor unit, a ground floor unit, a middle floor unit, and the unit with the largest testing-unit enclosure area. Each tested unit that fails adds three more. Buildings with fewer than eight testing units test every unit. Duct leakage and ventilation sampling follow Chapter 6 of the RESNET Mortgage Industry National Home Energy Rating Systems Standards. For how multifamily blower-door testing works in practice, see blower door testing multifamily buildings.
• Air barrier contact. Insulation in assemblies 60 degrees or more from horizontal must be in substantial contact with an air barrier on all sides, with an exception for air-impermeable insulation.
• Solar-ready and EV-ready appendices. Houston adopted Appendices CB and CD on the commercial side and RB and RD on the residential side. Under RD102.1, new residential parking facilities other than one- and two-family dwellings and townhouses follow the commercial EV provisions in Appendix CD.

Those are code-path facts, not design advice. Which ones bind your building depends on the 3-story split and the compliance method, which is exactly what should be settled before modeling hours are bought.

Proof From ECC Studies (Method, Not Houston Invoices)

ECC does not publish a Houston or Texas dollar-per-square-foot average, and we do not have a Houston COMcheck 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 Houston enforces. 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 Houston invoices. They show the order: lock the ASHRAE path, 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 Houston price.

Common Mistakes on Houston Multifamily Energy Filings

• Modeling to the statewide floor. Houston enforces the 2021 IECC and ASHRAE 90.1-2019 with local amendments, not the 2015 state minimum.
• Filing a four-story building as residential. Residential structures more than 3 stories are on the commercial provisions or ASHRAE 90.1-2019.
• Uploading an incomplete COMcheck. Missing certificates, a missing inspection checklist, unsigned statements, or default comments get rejected at prescreen.
• Forgetting the mechanical attachments. ASHRAE 183 load calculations and the commissioning form (or a claimed exemption) travel with the COMcheck.
• Using an unsealed performance report. A C407 total building performance report needs a Texas-licensed PE seal.
• Planning R-2 testing late. Sampling counts, unit selection, and re-test rules are in the amendments. Air sealing details that fail testing are cheaper to fix on paper.

When to Study First

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

1. Confirm the permit address is inside the City of Houston and on the 2021 Houston Construction Code
2. Lock the 3-story split: residential provisions for 3 stories or less, commercial or ASHRAE 90.1-2019 above that, and commercial documentation for nonresidential areas
3. Pick the compliance method for each portion: prescriptive, REScheck, ERI, COMcheck, or total building performance
4. Model envelope and HVAC packages side by side against that method, including ENERGY STAR Multifamily New Construction where you plan to enroll
5. Plan R-2 testing samples and commissioning scope before details freeze
6. Then produce the COMcheck certificates, ERI or REScheck 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 Houston energy code for multifamily is the 2021 IECC and ASHRAE 90.1-2019 with Houston amendments, in force since January 1, 2024. Multifamily 3 stories or less files on the residential provisions; taller residential and most mixed-use buildings file on the commercial provisions or ASHRAE 90.1-2019, usually with a COMcheck that Houston rejects at prescreen if it is incomplete. This is the Houston city-code door, not the statewide Texas code-path page and not the Texas study door. Lock the split and the method first, then buy the paperwork that matches the plan.