Services
The Test
What we do, how we do it, and what you need to have ready.
What Is a Duct Leakage Test?
A duct leakage test measures how much air escapes from an HVAC duct system under pressure. The test pressurizes the duct system to 25 Pa (0.1″ w.g.) with all registers sealed, then measures the airflow required to maintain that pressure, which equals the total leakage in CFM. That number is divided by the conditioned floor area to get leakage per 100 square feet, compared to the code threshold.
Who Needs a Test?
New York
- →Anyone installing ductwork in new construction. The New York State Energy Conservation Construction Code (ECCCNYS) R403.3.7 requires a test on every new residential duct system.
- →Contractors doing HVAC retrofits with new ductwork. Under ECCCNYS R503.1.2, any duct installation in an existing building triggers a test: duct replacement, new system additions, or extensions over 40 linear feet in unconditioned space.
- →Effectively everyone, as of the 2025 code (eff. 12/31/2025). The 2025 ECCCNYS eliminated the conditioned-space exemption, so nearly every new duct installation now requires testing.
Connecticut
Lower Fairfield County contractors face the same standard. The 2022 Connecticut State Building Code (effective October 1, 2022) adopts the 2021 International Energy Conservation Code (IECC) for residential energy provisions.
- →Duct testing required per IECC R403.3.5: Residential duct systems must be pressure tested for leakage. Like New York's 2025 update, the 2021 IECC removed the exemption for ducts located entirely within conditioned space.
- →Same method, same threshold: Tested at 25 Pa (0.1" w.g.) per ANSI/RESNET/ICC 380. Total leakage must not exceed 4.0 CFM per 100 sq ft of conditioned floor area (IECC R403.3.6).
Serving lower Fairfield County, CT: Greenwich, Stamford, Darien, New Canaan, and Norwalk.
New York Allowable Leakage
Table R403.3.8: Maximum Total Duct System Leakage
| Equipment & Duct Configuration | Serving more than 1,000 ft²(cfm / 100 ft²) | Serving 1,000 ft² or less(cfm, any number of returnsa) | |
|---|---|---|---|
| Number of ducted returnsa | |||
| < 3 | ≥ 3 | ||
| Space conditioning equipment is not installedb, c | 3 | 4 | 30 |
| All components of the duct system are installedc | 4 | 6 | 40 |
| Space conditioning equipment is not installed, but the ductwork is located entirely in conditioned spacec, d | 6 | 8 | 60 |
| All components of the duct system are installed and entirely located in conditioned spacec | 8 | 12 | 80 |
All values measured at 25 Pa (0.1" w.g.). For SI: 1 cfm/ft² = 0.0033 LPM/m²; 1 cfm = 28.3 LPM.
a. A ducted return is sheet-metal or flexible duct connecting return grilles to the return-side inlet of the air handler. Any other path from return or transfer grilles to the air handler does not count as a ducted return.
b. Testing is permitted with the equipment not installed, provided the return ductwork is installed and supply + return leakage is measured together.
c.For ducts in ventilated attics (or unvented attics with vapor diffusion ports) to count as "in conditioned space," leakage to outside must meet Item 2.1 of Section R403.3.4.
Source: ECCCNYS R403.3.8, Table R403.3.8 (2025 edition).
How Connecticut Differs
Connecticut is still on the 2021 IECC, which does not use this graduated table. CT sets a single total-leakage limit of 4.0 cfm per 100 ft² of conditioned floor area, with a higher 8.0 cfm per 100 ft²allowance where the duct system is entirely within conditioned space, measured at the same 25 Pa. It does not vary by number of ducted returns or by floor area the way New York's table does.
Our Equipment
Calibrated Fan
Retrotec US340X: used to pressurize the duct system and measure total leakage airflow in CFM.
Digital Manometer
Retrotec DM32X: measures the pressure differential across the duct system at 25 Pa.
Vent Caps & Tape
Used to seal all supply and return registers before pressurization.
Common Leak Locations
Ensure all ductwork connections, especially the boots and the air handler cabinet, are fully sealed to avoid a re-test.
Test Procedure: Step by Step
- 1
Schedule
You call or submit the form with the project address, number of systems, whether the air handler is installed, and your requested date. We confirm your scheduling quickly.
- 2
On-Site: Seal Registers
We seal all supply and return registers with vent caps or tape. We leave every opening in the duct system sealed except the connection point for the duct blaster.
- 3
Connect the Duct Blaster
We connect the duct blaster fan to the duct system at a return register opening or the air handler cabinet, then set the manometer to measure the pressure differential across the system.
- 4
Pressurize to 25 Pa
We adjust the fan until the duct system reaches exactly 25 Pa (0.1" w.g.). The airflow through the fan at that pressure is your total duct leakage in CFM.
- 5
Calculate Leakage Rate
We divide the leakage CFM by the conditioned floor area (in hundreds of square feet) to produce CFM/100 sf, then compare it to the applicable code threshold.
- 6
Pass/Fail Determination
We check your result against the ECCCNYS R403.3.8 thresholds: ≤ 3 CFM/100 sf (rough-in, air handler not installed) · ≤ 4 CFM/100 sf (rough-in, air handler installed) · ≤ 4 CFM/100 sf (post-construction).
- 7
Report Issued Same Day
Pass or fail, we complete the signed test report and hand it to you the same day. It includes all readings, the applicable threshold, test methodology (ANSI/RESNET/ICC 380), and a clear pass/fail determination. We also email you a digital copy.
What to Have Ready Before We Arrive
- ✓ Ductwork fully installed and connected
- ✓ Air handler installed or removed, either is fine, but affects which leakage threshold applies
- ✓ Access to the duct system (return register opening or air handler cabinet)
- ✓ Your tech on site: we strongly encourage your technician to be present to seal minor leaks and avoid a re-test
Duct sealing, insulation, and duct system design are not included. We test. We don't seal or repair.
If the System Fails
A failure is not a crisis. If the measured leakage exceeds the code threshold, the contractor has two options:
- AIf there is significant leakage, seal the ductwork and schedule a re-test on a separate day.
- BSpend the remainder of the two-hour test block sealing, then pay for additional 30-minute blocks so our technician can wait and keep testing until the system passes. Each additional 30-minute block is $40, and staying to pass on the same visit means you skip the separate $500 re-test fee entirely.
Re-test on the same project: $500, scheduled for a separate day once you've sealed the leaks. We issue the new signed report the same day we come back to re-test.
Key Code References
- ECCCNYS R403.3.7: Duct System Testing (2025 edition)
- ECCCNYS R403.3.8: Duct System Leakage (thresholds)
- ECCCNYS R503.1.2: Existing Buildings retrofit trigger
- 2021 IECC R403.3.5: Duct Testing (2022 CT State Building Code)
- 2021 IECC R403.3.6: Duct Leakage (CT thresholds)
- ANSI/RESNET/ICC 380: Required test methodology
- ASTM E1554: Alternative test standard
Testing is performed by a technician certified by the Building Performance Institute (BPI) in Infiltration & Duct Leakage (IDL), the nationally recognized credential for duct leakage measurement, under licensed PE oversight.