Quick answer. New Jersey adopted the 2024 energy code for low-rise homes on August 17, 2026. Permit applications submitted through February 17, 2027 can still be reviewed under the previous 2021 code. Under both editions a new home must pass a blower door test at 3.0 ACH50 or lower on the prescriptive path, and every duct system must be leak tested, including ducts inside conditioned space. The 2024 code changes how the duct limit is set and tightens the cap for performance-path homes.
Local Energy Audits tests for builders in New Jersey. Book a test online or call (888) 213-3975.
Which code applies to your project
| Complete permit application submitted | Code that applies |
|---|---|
| Before August 17, 2026 | 2021 energy code |
| August 17, 2026 through February 17, 2027 | Your choice: it may be reviewed under the 2021 code, or you can use the 2024 code |
| After February 17, 2027 | 2024 energy code |
“Low-rise residential” means one- and two-family homes and multifamily buildings of three stories or fewer.
What changed from the 2021 code to the 2024 code
| Requirement | 2021 code | 2024 code |
|---|---|---|
| Blower door limit, prescriptive path | 3.0 ACH50 | 3.0 ACH50 (unchanged) |
| Cap on performance and rating-index paths | 5.0 ACH50, or 0.28 CFM per sq ft | 4.0 ACH50, or 0.22 CFM per sq ft |
| Alternative for attached units and homes of 1,500 sq ft or less | 0.30 CFM per sq ft | 0.27 CFM per sq ft |
| Duct leakage limit | 4.0 CFM25 per 100 sq ft; 8.0 if entirely inside the envelope | A table based on number of returns and stage of installation (3 to 12) |
| Additional efficiency | One package option | 10 credits |
| Prescriptive ceiling insulation | R-60 | R-49 |
New Jersey’s amendments to the residential chapter are administrative. The state describes them as making no technical changes, so the testing rules apply as written in the 2024 code.
Blower door test requirements (2024 code)
A blower door test measures how much air leaks through the shell of the house. The result is reported in ACH50: air changes per hour at a test pressure of 50 pascals. Lower is tighter.
| Compliance path | Maximum air leakage |
|---|---|
| Prescriptive | 3.0 ACH50 |
| Performance or Energy Rating Index | 4.0 ACH50, or 0.22 CFM per sq ft of building envelope area |
| Attached units tested individually, and buildings of 1,500 sq ft or less | May instead meet 0.27 CFM per sq ft |
The 3.0 limit applies in both of New Jersey’s climate zones.
- Tested to ANSI/RESNET/ICC 380, ASTM E779, ASTM E1827 or ASTM E3158.
- Run after all penetrations of the building envelope are sealed.
- Written up in a report signed by the tester and given to the code official.
Duct leakage test requirements (2024 code)
Every duct system is tested, at rough-in or after construction, to ANSI/RESNET/ICC 380 or ASTM E1554. Ducts inside conditioned space are not exempt; they get a higher allowance.
Maximum total duct leakage
| Equipment and duct configuration | Fewer than 3 ducted returns | 3 or more ducted returns | System serving 1,000 sq ft or less |
|---|---|---|---|
| Space conditioning equipment not installed | 3 CFM25 per 100 sq ft | 4 CFM25 per 100 sq ft | 30 CFM25 total |
| All duct system components installed | 4 | 6 | 40 |
| Equipment not installed, ductwork entirely in conditioned space | 6 | 8 | 60 |
| All components installed and entirely in conditioned space | 8 | 12 | 80 |
Points builders miss:
- A “ducted return” has to be an actual duct. Sheet metal or flex duct from a return grille to the air handler counts. Any other way of moving return air to the air handler does not.
- Ducts in a vented attic are not “in conditioned space” unless they are buried in the ceiling insulation and meet a separate leakage-to-outside limit.
- If the air handler’s location in conditioned space can’t be verified before the certificate of occupancy, the system has to be retested.
The only exception from testing is for ducts that serve a ventilation system and are not tied into the heating or cooling ducts.
If your project is still under the 2021 code
- Blower door: 3.0 ACH50 on the prescriptive path; no result above 5.0 ACH50 on any path.
- Duct leakage: 4.0 CFM25 per 100 sq ft with the air handler installed, 3.0 without it, 4.0 after construction, and 8.0 where the ducts and air handler are entirely inside the envelope.
- Ducts are tested regardless of where they are located.
Climate zones by county
| Zone | Counties |
|---|---|
| 4A | Atlantic, Burlington, Camden, Cape May, Cumberland, Essex, Gloucester, Hudson, Mercer, Middlesex, Monmouth, Ocean, Salem, Union |
| 5A | Bergen, Hunterdon, Morris, Passaic, Somerset, Sussex, Warren |
The zone affects insulation and window requirements. It does not change the blower door or duct limits above.
Who can perform the tests
New Jersey does not issue a tester license. Under the state’s currently issued guidance (Bulletin 22-1):
- The blower door test is documented by a person independent of the installer, a third party, who is approved by the local code official.
- The code sets no specific credential for the tester.
- The same third party can also verify the air barrier checklist.
So approval is local. Ask your construction office whether it has requirements or a list.
Ori Rosenkrantz of Local Energy Audits holds the BPI Infiltration and Duct Leakage certification and tests as an independent third party.
Need a third-party tester in New Jersey?
Blower door and duct leakage tests for builders, with the signed report your code official needs.
What your code official needs
- The Air Barrier and Insulation checklist (Form UCC-F392), with the blower door result attached.
- The signed duct leakage report. You choose whether to test at rough-in or after construction.
- The energy efficiency certificate posted in the home.
Ask about report timing when you book.
Additions. Under the state’s guidance, a blower door test is not required for an addition if the visual air barrier inspection is complete.
Tips for passing the first time
General guidance, drawn from the code’s own air barrier and testing requirements.
- Seal before you cover. Air sealing is cheapest while framing is open. Work through the code’s air barrier checklist before insulation and drywall go in.
- Check the places the code’s air barrier table names. Top plates and attic penetrations, the attic hatch, recessed lights, rim joists, the wall between house and garage, tubs and showers on exterior walls, electrical boxes, and duct boots.
- Call for the test at the right time. The blower door test is run after every penetration of the building envelope is made and sealed. Leave time before final inspection for a re-test.
- Have the house ready. Windows and exterior doors installed and closed, interior doors open, and heating and cooling equipment off.
- Seal ducts while you can reach them. Seal joints, seams and boots before they are covered. A rough-in test finds leaks while they are still easy to fix.
- Count your ducted returns. Under the 2024 code the duct leakage target depends on whether the system has fewer than three ducted returns or three or more. Know which row of the table applies before the test.
Frequently asked questions
What ACH50 do I need to pass a blower door test in New Jersey?
3.0 ACH50 or lower on the prescriptive path, in every county. On the performance or Energy Rating Index path the cap is 4.0 ACH50 under the 2024 code.
Which energy code applies to my New Jersey project right now?
The 2024 code took effect August 17, 2026. A complete permit application submitted through February 17, 2027 can still be reviewed under the 2021 code. After that date only the 2024 code applies.
Is a duct leakage test required in New Jersey if my ducts are inside conditioned space?
Yes. Every duct system is tested. Ducts and equipment entirely in conditioned space get a higher allowance: 8 CFM25 per 100 square feet, or 12 with three or more ducted returns, under the 2024 code.
Who can perform a blower door test in New Jersey?
A third party who is independent of the installer and approved by your local code official. The state sets no specific credential.
How many returns does my duct system need to get the higher leakage allowance?
Three or more ducted returns. Each must be a real duct connecting a return grille to the air handler.
Do I need a blower door test for an addition?
Under the state’s guidance, no, as long as the visual air barrier inspection is complete. Confirm with your construction office.
Is my county in climate zone 4A or 5A?
Bergen, Hunterdon, Morris, Passaic, Somerset, Sussex and Warren are 5A. Every other county is 4A. The blower door and duct limits are the same in both.
What happens if the house fails?
The leaks are found and sealed, and the house is tested again. Call (888) 213-3975 to arrange a re-test.
Sources
- NJ Department of Community Affairs: adoption of the 2024 model codes, 58 N.J.R. 8(2)
- NJ DCA: Construction Code Communicator, Fall 2026
- NJ DCA: rule proposal for the 2024 codes
- NJ DCA: Bulletin 22-1, Energy Subcode Compliance
- NJ DCA: list of currently issued bulletins
- 2024 International Energy Conservation Code, Chapter 4 (Residential)
- 2021 International Energy Conservation Code, Chapter 4 (Residential)
- US Department of Energy: New Jersey energy code status
This page summarizes the code for builders and is not legal advice. Confirm the details of your project with your local construction office.
Code requirements elsewhere: Pennsylvania · Philadelphia · Delaware
Our services: Blower door testing · Duct leakage testing