New Jersey Adopts 2024 IECC: What Design and Construction Professionals Need to Know
November 3, 2026New Jersey adopted the 2024 International Energy Conservation Code (IECC) without amendments to the model code’s provisions on August 17, 2026 with a 6-month grace period. Projects permitted on or after February 17, 2027 will need to meet the new code version. The state excluded the commercial provisions of the 2024 IECC from adoption, leaving ASHRAE 90.1-2022 as the compliance standard for commercial projects, consistent with previous code cycles. The state also adopted all appendices, which are optional at the discretion of the permit holder.
Understanding the updated requirements early in the design process can help teams avoid costly changes, coordinate documentation, and keep projects moving.
Which NJ Energy Code Applies to Your Project?
New Jersey uses different energy code standards depending on the type of building:
- Residential: The 2024 IECC residential code applies to low-rise residential buildings three stories or less, including one- and two-family dwellings, townhouses, and multifamily buildings.
- Commercial: ASHRAE Standard 90.1-2022 applies to commercial buildings and other residential buildings that fall outside the low-rise residential category, including multifamily buildings four stories or more.
NJ Residential Energy Code: Key Changes
The following are some of the key changes from the 2021 to the 2024 IECC that residential design and construction professionals should understand.
1. Sampling Is Now Permitted for Certain Multifamily Testing (R402.5.1.2, R403.3.9, R403.6.4)
For multifamily buildings with eight or more units, the 2024 IECC allows sampling for certain required tests, including:
- Building envelope air leakage (blower door) testing
- Duct leakage testing
- Mechanical ventilation testing
Under the 2024 IECC, the sampling protocols for these tests require: :
- Building must contain 8 units or more
- Must test 7 units or 20% of the units, whichever is greater
- Tested units shall include a top-floor unit, a ground-floor unit, a middle-floor unit and the dwelling unit or sleeping unit with the largest testing unit enclosure area
- If a unit in the sample does not pass, an additional 3 units must be tested, including the corrected unit
Sampling may help reduce the number of individual tests required on qualifying projects. Before testing begins, project teams should confirm that their sampling method adheres to the protocol and that all required units are included in the testing plan.
2. Duct Leakage Testing Thresholds are Now Mandatory (R403.3.8)
The 2024 IECC requires projects meet mandatory total duct leakage testing thresholds regardless of the compliance pathway selected.
The code outlines the maximum allowable total duct leakage for residential projects based on duct location, whether the system includes an air handler, and the number of return ducts. Duct systems located entirely within conditioned space are permitted higher leakage limits than systems with ducts in unconditioned areas. The allowable leakage also increases when a system has more than three return ducts.
The allowable leakage threshold does not change between pathways, making it important for project teams to plan for testing and ensure duct systems are properly sealed.
Early coordination between mechanical contractors, builders, and testing professionals can help identify potential issues before testing.
2024 IECC Residential Maximum Total Duct Leakage Thresholds
| < 3 Returns Ducts | > 3 Return Ducts | |
| Ducts in unconditioned space | ||
| No Air Handler | 3% | 4% |
| W/ Air Handler | 4% | 6% |
| Ducts in 100% conditioned space | ||
| No Air Handler | 6% | 8% |
| W/ Air Handler | 8% | 12% |
3. New Mechanical Ventilation and Exhaust Fan Requirements (R403.6.2)
The updated code introduces additional requirements for ventilation equipment and controls, including:
- Fan efficiency: Minimum efficiency requirements now apply to mechanical ventilation and outdoor air ventilation fans.
- Testing: Previously, third-party testing was required only for mechanical ventilation systems. The updated code expands testing requirements to include all supply and exhaust fans, including bathroom and kitchen exhaust fans.
- Bathroom exhaust controls: Intermittent bathroom exhaust fans must have automatic shutoff controls, such as a timer, occupancy sensor, humidity sensor, or contaminant control. An exception applies to qualifying fans that are part of the home’s mechanical ventilation system.
These requirements make it important to consider ventilation equipment, controls, and testing needs during design and installation.
4. Updated Lighting Efficiency and Controls (R404.2.2, R404.2.1, R404.2.2, Table R404.1)
The 2024 IECC introduces new lighting efficiency and control requirements across residential compliance pathways.
Key changes include:
- Lighting efficacy: Permanently installed lighting must meet the minimum efficacy requirements of 45 lumens per watt or shall contain lamps capable of operation with an efficacy of not less than 65 lumens per watt.
- Habitable spaces: Lighting in habitable spaces must be controlled by a manual dimmer or an automatic shutoff control.
- Utility spaces: Permanently installed lighting in garages, unfinished basements, laundry rooms, and utility rooms must have automatic shutoff controls.
- Exterior lighting: New lighting power allowances limit the amount of exterior lighting permitted.
Project teams should account for these requirements when selecting fixtures and planning lighting controls.
NJ Commercial Energy Code: Key Changes
For commercial projects, New Jersey has adopted ASHRAE Standard 90.1-2022, replacing the previously referenced ASHRAE Standard 90.1-2019. The state adopted the standard unamended. The 2022 standard includes updates to building envelope requirements, mechanical systems, lighting, energy modeling, and renewable energy. Here are several areas that commercial design and construction professionals should review.
1. Building Envelope and Air Leakage (Section 5.4.3.1)
New buildings with less than 10,000 square feet of gross conditioned floor area must undergo whole-building air leakage testing to demonstrate compliance with the specified leakage limit.
For buildings with 10,000 square feet or more, projects may meet the requirement through either air leakage testing or envelope commissioning. This gives larger projects an alternative to whole-building testing, but requires additional planning and documentation to demonstrate compliance.
The maximum allowable air leakage rate has also decreased from 0.40 to 0.35 cfm/ft², tightening the standard for building envelope performance.
2. Renewable Energy (Section 10.5.1.1)
ASHRAE 90.1 2022 introduces a prescriptive requirement for on-site renewable energy systems, adding a new consideration for project teams evaluating compliance options. Qualifying buildings must provide on-site renewable energy equipment with a rated capacity of at least 0.50 W/ft², multiplied by the gross conditioned floor area of up to the three largest floors.
The main exceptions include:
- Smaller projects: New construction or additions where the combined gross conditioned floor area of the three largest floors is less than 10,000 square feet.
- Limited usable roof space: More than 80% of the roof area is covered by qualifying equipment or other listed uses, such as planters, vegetated space, skylights, or occupied roof decks.
- Significant shading: More than 50% of the roof is shaded from direct sunlight by natural objects or structures outside the building for more than 2,500 hours annually.
- Alterations: Alteration projects that do not include additions are exempt.
Because renewable energy is now part of the prescriptive requirements, teams should evaluate available roof area, system capacity, and applicable exceptions early in design, particularly when comparing compliance strategies. Commercial projects may benefit from using energy modeling to comply via a performance-based pathway and potentially reduce or eliminate the need to purchase off-site renewable energy.
3. Expanded Commissioning Requirements (Section 4.2.5)
Although commissioning was already required under ASHRAE 90.1-2019, more detailed compliance documentation and verification requirements for various systems are now in effect. ASHRAE 90.1 2022 now outlines the commissioning process as:
- Creation of a commissioning plan submitted to owner and with the building permit application as requested
- Design review report
- Preparation and submission of a preliminary commissioning report
- Functional performance testing (FPT) of HVAC equipment and controls, economizers, lighting controls, and service water heating systems, as applicable
- Completion of systems adjusting and balancing
- Final commissioning report
- Owners must provide building officials with either a copy of the reports or transmittal letter confirming the owner’s receipt and acceptance of all required verification, FPT, and preliminary commissioning documentation.
The commissioning provider must be (a) a third-party entity not associated with the building project, (b) owner’s qualified employees, or (c) an individual associated with the design firm or contractor but not directly associated with design or installation of the building systems, controls, or building envelope being commissioned.
These requirements make it important to identify the commissioning provider early and incorporate commissioning activities into the construction documents and project schedule.
4. New Energy Credit Requirements (Section 11.5.1)
ASHRAE 90.1-2022 introduces a prescriptive energy credit system that requires projects to achieve additional efficiency beyond the standard’s baseline requirements. The standard offers a range of efficiency measures across building systems, including HVAC and lighting, allowing design teams to select options that contribute a specified number of credits toward the project’s required total.
The number of credits assigned to each measure varies by building type and climate zone. Because the required credits and eligible measures vary by project, teams should evaluate the options early to understand how they may affect design decisions, costs, and energy performance.
As a result, standard COMcheck inputs alone may not be sufficient to demonstrate full compliance; additional analysis and documentation may be necessary to account for the applicable credit requirements. Energy modeling and performance-based compliance pathways offer more flexibility in decision making.
5. Updated Performance Pathway Requirements (Appendix G and Chapter 12)
The 2022 standard includes updates to its performance-based compliance pathways, including the Energy Cost Budget Method in Chapter 12 (formerly Chapter 11) and the Performance Rating Method in Appendix G. These updates affect how proposed buildings and baseline energy models are evaluated, including modeling assumptions for HVAC systems, lighting, building envelope performance, renewable energy, and energy efficiency credits.
Chapter 12 compares the proposed building against a baseline that generally reflects the same design while meeting the applicable prescriptive requirements of the 2022 standard.
Appendix G uses a standardized baseline based on 2004-era building efficiency, with performance targets designed to remain consistent across code editions. The new 90.1 standard makes multifamily buildings on average 10% more efficient than the previous version.
Both pathways also establish rules for modeling renewable energy systems and accounting for energy efficiency measures when demonstrating compliance. For projects pursuing performance-based compliance, energy modeling should be incorporated early in the design process. This allows teams to evaluate options, understand the impact of design decisions, and identify a practical pathway to compliance.
Plan Ahead for New Jersey Energy Code Changes
The transition to the 2024 IECC and ASHRAE 90.1-2022 brings new requirements for residential and commercial projects across New Jersey. Understanding the requirements early can help teams avoid delays, save costs, and make informed design decisions.
At ReVireo, we work with architects, engineers, developers, builders, and contractors to navigate energy code compliance from design through construction. Our team can help identify applicable requirements, evaluate compliance pathways, coordinate required testing and verification, and address potential issues before they become costly.
Have an upcoming project in New Jersey? Reach out to ReVireo to discuss your energy code compliance needs and how we can help your team plan for the updated requirements.