FAQ
Duct Leakage Testing: Common Questions
Code requirements, test procedures, pricing, and what to expect.
Is duct leakage testing required in New York State?
Yes. The NYS Energy Conservation Construction Code (ECCCNYS) Section R403.3.7 (2025 edition, effective December 31, 2025) requires duct leakage testing for all residential duct installations. The previous 2020 ECCCNYS Section R403.3.3 imposed the same requirement. A written report signed by the party conducting the test must be provided to the code official.
Is duct leakage testing required in Connecticut?
Yes. The 2022 Connecticut State Building Code (effective October 1, 2022) adopts the 2021 International Energy Conservation Code (IECC). IECC Section R403.3.5 requires duct leakage testing for residential duct systems, and the 2021 IECC removed the exemption for ducts located entirely within conditioned space, the same change New York made. Total leakage must not exceed 4.0 CFM per 100 sq. ft. of conditioned floor area (IECC R403.3.6), measured at 25 Pa (0.1" w.g.) per ANSI/RESNET/ICC 380. We serve lower Fairfield County, including Greenwich, Stamford, Darien, New Canaan, and Norwalk.
Are there common leak locations?
Yes. The air handler cabinet itself and where the boots connect to the registers are the two most common sources of leakage. Ensure all ductwork connections, especially the boots and the air handler cabinet, are fully sealed to avoid a re-test.
Does the NYS energy code require duct testing on HVAC retrofits?
Yes. ECCCNYS Section R503.1.2 (Existing Buildings, Heating and Cooling Systems) requires that new duct systems installed as part of an alteration comply with Section R403.3, including duct testing. This means any residential HVAC retrofit involving new ductwork, duct replacement, system additions, or duct extensions beyond 40 linear feet in unconditioned space, triggers the testing requirement. This applies in Westchester, Rockland, and Putnam Counties and throughout New York State.
What is the maximum allowable duct leakage in NYS?
Per ECCCNYS R403.3.8 (2025 edition), the maximum allowable leakage is: 3 CFM per 100 sq. ft. of conditioned floor area for a rough-in test when the air handler is not installed; 4 CFM per 100 sq. ft. for a rough-in test with the air handler installed; and 4 CFM per 100 sq. ft. for a post-construction test. All measurements are taken at 25 Pa (0.1" w.g.) with registers sealed.
What equipment is used for a duct leakage test?
A duct leakage test requires a calibrated duct blaster (a variable-speed fan used to pressurize the duct system), a digital manometer (to measure pressure differential, typically a DG-1000 or DM32X), flexible duct connectors, and vent caps or tape to seal registers. A smoke generator is used when identifying leak locations after a failure. Test methodology follows ANSI/RESNET/ICC 380.
Who is qualified to perform a duct leakage test?
Duct leakage testing should be performed by a technician with recognized certification in airtightness and duct leakage measurement. Our testing is performed by a technician certified by the Building Performance Institute (BPI) in Infiltration & Duct Leakage (IDL), the nationally recognized credential for this work, under the oversight of Marcy Engineering, PLLC, a licensed New York professional engineering firm. BPI is accredited by the American National Standards Institute (ANSI). The combination of BPI IDL certification and PE oversight means the signed report carries weight with building officials.
What is the difference between a rough-in test and a post-construction test?
A rough-in test is performed before interior finishes are complete: ductwork is installed and accessible, but walls and ceilings may still be open. This allows leak locations to be identified and sealed more easily. A post-construction test is performed after the building is complete. The leakage threshold is the same for both (4 CFM/100 sf at 25 Pa), except for rough-in tests without the air handler installed, where the threshold is 3 CFM/100 sf. Most contractors in Westchester County schedule the rough-in test.
What happens if my ductwork fails the leakage test?
If measured leakage exceeds the applicable threshold, the system fails. We use a smoke generator to identify the specific leak locations: typically unsealed joints, disconnected flex duct connections, or improperly taped seams. The contractor seals the identified leaks with mastic sealant or UL 181-rated foil tape. We then schedule a re-test on a separate day, typically within a day or two, at a reduced rate of $500. We issue a new signed test report at the re-test.
How long does a duct leakage test take?
On-site time is typically 30–45 minutes per duct system for a standard residential installation. This includes register sealing, equipment setup, pressurization, measurement, and report completion. A two-system house (separate upstairs and downstairs duct systems) typically takes 60–90 minutes on-site.
Does duct testing apply to ducts inside conditioned space?
Under the 2025 ECCCNYS (effective December 31, 2025), yes. The 2020 ECCCNYS contained an exemption for duct systems located entirely within the building thermal envelope (conditioned space). The 2025 update eliminates that exemption. All new residential duct installations, regardless of location, now require testing. This significantly expands the pool of projects that require testing.
What is ANSI/RESNET/ICC 380?
ANSI/RESNET/ICC 380 is the 'Standard for Testing Airtightness of Building Enclosures, Airtightness of Heating and Cooling Air Distribution Systems, and Airflow of Mechanical Ventilation Systems.' The 2025 ECCCNYS references this standard as the required test methodology for duct leakage testing. It replaced the prior practice of referencing ASTM E1554, though ASTM E1554 remains an acceptable alternative standard.
Do I need duct testing for a duct extension under 40 linear feet?
Under the 2020 ECCCNYS, duct extensions of 40 linear feet or less in unconditioned space were exempt from testing requirements in existing buildings (per R503.1.2). The 2025 ECCCNYS narrowed the retrofit exemptions. If your project involves replacing a duct system or installing more than 40 linear feet of new duct in unconditioned space as part of an alteration, testing is required. For borderline projects, confirm with the local building department.
Which Westchester building departments require duct testing?
Every Westchester County municipality enforces the New York State Energy Conservation Construction Code, which requires duct testing for qualifying new duct installations. White Plains, Yonkers, New Rochelle, Mount Vernon, and Peekskill have their own city-level enforcement. Most Westchester towns and villages run their own building departments. In practice, any HVAC permit that includes new ductwork should plan for a duct test as part of the permit close-out process.
How much does duct leakage testing cost in Westchester County?
Standard testing is $600 per duct system, and re-tests on the same project after contractor seals are $500. All pricing is to the contractor. Contractors running multiple jobs per month can apply for a Trade Partner account for volume pricing: submit the Trade Partner form and we'll follow up with rates. See our full pricing page for details.
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