Energy codes feel boring until they bite you. Sloppy HVAC installs that skip Manual J, use undersized ducts, or install non-compliant equipment can void your homeowners insurance, block a home sale, and trigger expensive forced removal of equipment. Even in jurisdictions with light enforcement, code compliance protects long-term home value.
Here is how the two main US energy codes work, what each requires for HVAC, which states follow which edition, and how to verify your contractor is compliant.
IECC vs ASHRAE 90.1: What Each Covers
Two main US model energy codes:
| Code | Published By | Covers | Update Cycle |
|---|---|---|---|
| IECC | International Code Council (ICC) | Residential (1 to 3 stories) and commercial | 3-year cycle |
| ASHRAE 90.1 | ASHRAE | Commercial and multifamily (4+ stories) | 3-year cycle |
Most homeowners deal with IECC for residential work. ASHRAE 90.1 matters for commercial buildings and large multifamily projects. The two codes track closely on HVAC equipment efficiency (both reference federal DOE minimums) but differ on building envelope and ventilation requirements.
What IECC Requires for HVAC
Current IECC residential HVAC requirements include:
- Equipment efficiency: meets federal DOE minimums (14.3 SEER2 / 7.5 HSPF2 for split heat pumps, 80 to 95% AFUE for furnaces depending on climate zone)
- Manual J load calculation: required for new equipment sizing (IECC R403)
- Manual S equipment selection: equipment must match calculated load within 25%
- Manual D duct sizing: ducts must deliver design airflow at acceptable pressure drop
- Duct sealing: 4 CFM per 100 sq ft of conditioned floor area max leakage at 25 Pa
- Duct insulation: R-8 minimum in unconditioned spaces, R-6 in conditioned spaces
- Programmable thermostat: required for primary heating and cooling systems
- Refrigerant charge verification: required at install with manufacturer-spec method
- Building air tightness: 5.0 ACH at 50 Pa or lower (3.0 ACH in zones 3-8 under 2024 IECC)
Most of these are verified during the permit inspection process. Stamped Manual J reports are increasingly required by inspectors before they sign off.
IECC State Adoption Status
States adopt the IECC at different rates. Some skip editions; some amend them; a few reject IECC entirely. Current status:
| IECC Edition | States Using It |
|---|---|
| 2024 IECC | CO, IL, RI; pending in CT, DE, ME, MD, MA, NJ, NY |
| 2021 IECC | Most US states (about 25) |
| 2018 IECC | Most southern states (TX, FL, GA, etc.) |
| 2015 IECC or older | A few states still on older editions |
| State-specific code (not IECC) | California (Title 24), Florida (FBC EC) |
| No statewide code | Mississippi, Wyoming, Missouri (local choice) |
Check your state energy office and local building department for the specific code edition that applies to your project. Local amendments often modify state-level adoption further.
What Changed in IECC 2024
Notable changes from 2021 to 2024 IECC that affect HVAC:
- R-60 attic insulation in zones 4 through 8 (up from R-49)
- Lower window U-factors in cold climates (0.21 in zone 8, down from 0.26)
- Tighter air sealing: 3.0 ACH at 50 Pa in zones 3-8 (down from 5.0)
- Demand-control ventilation required for spaces with variable occupancy
- Energy recovery ventilator (ERV) requirements for buildings with significant exhaust airflow
- Electric-ready provisions in some adoptions: pre-wiring for future heat pump and EV charger installs
- Updated duct leakage testing requirements and stricter compliance documentation
- Manual J version reference updated to ACCA Manual J 8th edition
If you are in a state that has adopted 2024 IECC, expect somewhat higher install costs due to better insulation and air sealing requirements. Long-term operating savings are meaningful enough that the trade-off generally pencils out.
Equipment Efficiency Requirements
Federal DOE sets minimum efficiency for HVAC equipment manufactured for sale in the US. IECC and ASHRAE 90.1 reference these federal minimums. Current requirements as of today:
| Equipment | Current Minimum | Next Update |
|---|---|---|
| Split-system AC | 14.3 SEER2 (north), 15.2 SEER2 (south) | 2029 (likely 16+ SEER2) |
| Split-system heat pump | 14.3 SEER2 / 7.5 HSPF2 | 2029 |
| Gas furnace (northern states) | 90%+ AFUE | 95% nationwide Jan 2028 |
| Gas furnace (southern states) | 80%+ AFUE | 95% nationwide Jan 2028 |
| Packaged AC (commercial) | 14 to 16 IEER depending on size | 2027 |
| Geothermal heat pump (closed-loop) | 3.6 COP / 17.1 EER (ENERGY STAR) | TBD |
Refrigerant transition to R-454B (A2L class, mildly flammable, lower global warming potential) became mandatory for new equipment manufactured in 2025. This is a separate federal EPA rule, not part of IECC, but it affects installation requirements: leak detection sensors, charge limits, and tech certification.
How Code Compliance Is Enforced
The permit and inspection process is the main enforcement mechanism. A typical compliance sequence:
- Permit application: contractor files with the local building department, includes Manual J calculation, equipment specs, and AHRI certification.
- Plan review: building department reviews the application for code compliance before issuing the permit.
- Rough inspection: if applicable, inspector verifies ductwork, gas line, refrigerant line set, and electrical before walls are closed.
- Final inspection: inspector verifies equipment installation, refrigerant charge, duct leakage test results, electrical connection, condensate drain, thermostat operation.
- Certificate of occupancy update: the permit closure becomes part of the home's permanent record, available to future buyers and lenders.
Strict jurisdictions (California, Massachusetts, New York, Washington) require third-party verification, blower door tests, and duct leakage tests. Light enforcement jurisdictions may only require the permit pull and one inspector visit.
What Skipping the Permit Costs You
Unpermitted HVAC work seems like a money saver until something goes wrong. Real costs of skipping the permit:
- Voided homeowners insurance: if a fire or other claim involves the HVAC system, insurance can deny payment
- Blocked home sale: buyers inspectors flag unpermitted work, lenders require it resolved before closing
- Forced equipment removal: some jurisdictions require unpermitted HVAC to be torn out and reinstalled correctly
- Fines: $500 to $5,000+ depending on jurisdiction
- Voided manufacturer warranty: most warranties require professional installation by an authorized dealer with proper permits
- Future tax credit ineligibility: federal tax credits required permitted installations (now expired but historical issue)
Permit fees are $100 to $500. Reputable contractors include the permit in their quote automatically. If a contractor offers a discount to skip the permit, walk away.
How to Verify Your Install Is Code-Compliant
Five questions to confirm your contractor is doing code-compliant work:
- "What IECC edition does my jurisdiction enforce?" They should know.
- "Are you pulling a permit? Can I see it after it's issued?" Yes and yes.
- "Did you do a Manual J load calculation? Can I see the report?" Yes to both.
- "What is the AHRI certification number for the indoor and outdoor units?" Look it up at ahridirectory.org to confirm the components are a matched pair.
- "Will you perform a duct leakage test and give me the results?" Required under most current IECC editions; should be included.
If your contractor cannot answer these, find a different contractor. Pressure-test the full quote with our HVAC quote analyzer before signing.
Bottom Line
Energy codes are not optional. IECC and ASHRAE 90.1 set the minimum efficiency requirements for HVAC installation in nearly every US jurisdiction. Compliance is enforced through permits and inspections, and skipping the process exposes you to insurance and resale problems.
Confirm your contractor pulls a permit, runs a Manual J load calculation, uses AHRI-matched equipment, and performs the required duct leakage test. Find out which IECC edition your jurisdiction uses (or whether you are in California Title 24 territory) before any major HVAC project. Code compliance protects your home value and your safety.