Services
The Duct Leakage Test Process
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.
The test is required by the NYS Energy Conservation Construction Code (ECCCNYS) for all residential duct installations — new construction and retrofits. A signed written report is required by the code official before a certificate of occupancy is issued.
When Is Testing Required?
- →New construction with duct systems: Required per ECCCNYS R403.3.7.
- →HVAC retrofits with new ductwork: Required per ECCCNYS R503.1.2. Any duct installation in an existing building — duct replacement, new system additions, extensions over 40 linear feet in unconditioned space — triggers the requirement.
- →2025 code update (eff. 12/31/2025): The 2025 ECCCNYS eliminates the conditioned-space exemption that previously existed. Virtually all new duct installations now require testing.
Equipment
Duct Blaster
Calibrated fan used to pressurize the duct system and measure leakage airflow in CFM.
Digital Manometer
DG-1000 or DM32X — measures pressure differential across the duct system at 25 Pa.
Vent Caps & Tape
Used to seal all supply and return registers before pressurization.
Smoke Generator
Used to identify leak locations when a system fails, before re-sealing and re-test.
Test Procedure — Step by Step
- 1
Schedule
Contractor calls or submits form. Provides project address, number of systems, whether AHU is installed, and requested date. We confirm same or next day.
- 2
On-Site: Seal Registers
Technician seals all supply and return registers with vent caps or tape. Every opening in the duct system must be sealed except the connection point for the duct blaster.
- 3
Connect the Duct Blaster
The duct blaster fan is connected to the duct system at a return register opening or AHU cabinet. The manometer is set to measure the pressure differential across the system.
- 4
Pressurize to 25 Pa
The fan is adjusted until the duct system reaches exactly 25 Pa (0.1" w.g.). The airflow through the fan at that pressure is the total duct leakage in CFM.
- 5
Calculate Leakage Rate
Leakage CFM is divided by the conditioned floor area (in hundreds of square feet) to produce CFM/100 sf. This is compared to the applicable code threshold.
- 6
Pass/Fail Determination
Thresholds per ECCCNYS R403.3.8: ≤ 3 CFM/100 sf (rough-in, AHU not installed) · ≤ 4 CFM/100 sf (rough-in, AHU installed) · ≤ 4 CFM/100 sf (post-construction).
- 7
Report Issued On-Site
Pass or fail, the signed test report is completed on-site and handed to the contractor before we leave. It includes all readings, the applicable threshold, test methodology (ANSI/RESNET/ICC 380), and a clear pass/fail determination. A digital copy is emailed.
What to Have Ready Before We Arrive
- ✓ Ductwork fully installed and connected
- ✓ All registers and grilles in place (we seal them)
- ✓ AHU installed or removed — either is fine, but affects which leakage threshold applies
- ✓ Conditioned floor area (sq. ft.) for the zone being tested
- ✓ Access to the duct system (return register opening or AHU cabinet)
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, we use the smoke generator to identify leak locations — joints, seams, improperly sealed connections. The contractor seals the identified leaks with mastic or foil tape, and we schedule a re-test.
Re-test on the same project: $200. Same-day re-test if schedule permits; next-day guaranteed. We issue a new signed report on-site after the 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
- ANSI/RESNET/ICC 380 — Required test methodology
- ASTM E1554 — Alternative test standard
Ready to schedule?
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