Duct Leakage Test
CFM25 duct leakage testing for IECC, ENERGY STAR, and HERS compliance. NCI-certified field techs, 6-state service area.
NCI Certified
RESNET Certified
IBHS FORTIFIED
Since 2009
6-State Service
Fixed-Fee Quotes
A duct leakage test measures how much air your HVAC ducts lose to the outside, attic, basement, or crawlspace. Leaky ducts can waste 20-30% of your heating and cooling energy. HECS runs residential and light-commercial duct leakage tests across Kentucky, Ohio, Indiana, Tennessee, Illinois, and Missouri.
What is Duct Leakage Test?
Duct leakage is measured with a calibrated fan (Duct Blaster) connected to the duct system at the air handler. The fan depressurizes (or pressurizes) the ducts to a standard 25 Pascals of pressure difference. The airflow in cubic feet per minute at 25 Pa is the total duct leakage, expressed as CFM25.
There are two metrics:
CFM25 to outside (CFM25-O): the leakage that goes to unconditioned space (attic, basement, garage, crawlspace). This is the metric code officials and HERS raters care about.
Total CFM25: leakage total, including leakage inside the conditioned space. This is easier to test but less useful.
The 2018 IECC (Section R403.3.3) requires total duct leakage ≤5 CFM25 per 100 sq ft of conditioned floor area, with ≤1.5 CFM25 to outside for homes in Climate Zones 1-2. ENERGY STAR v3 requires CFM25-O ≤5% of nominal airflow. Most leaky existing homes test 15-30% of nominal airflow — meaning 15-30% of the furnace / AC output is heating or cooling the attic instead of the home.
Who needs duct leakage test?
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Builders needing 2018/2021 IECC Section R403.3.3 compliance for total and outdoor duct leakage.
HERS raters and program reviewers using duct leakage results to model energy use.
ENERGY STAR v3, NGBS Green, and EarthCraft projects requiring a sealed, tested duct system.
Homeowners with high utility bills, room-to-room temperature swings, or comfort problems.
Multifamily developers needing mid-rise duct leakage verification (per-unit and total building).
HECS’s process for duct leakage test
- System identification (10 min). HECS tech identifies the air handler, supply trunks, return trunks, and any zone dampers. We also seal all supply and return registers with magnetic covers or painter’s tape so the test isolates duct leakage only.
- Duct Blaster setup (5 min). Duct Blaster fan mounts to the air handler cabinet (or a return grille), speed controller set to 25 Pa. Multi-point test gives the leakage curve used for IECC compliance and HERS modeling.
- Total leakage test (5 min). Pressurize to 25 Pa and read total CFM25. This is the whole-system leakage including leakage to conditioned space.
- Leakage-to-outside test (15-20 min). With the duct system pressurized to 25 Pa and the home depressurized to 50 Pa (using the blower door at the same time), the tech walks the home with a thermal camera to find and quantify each leak from the duct system to outside. Result is CFM25-O.
- Certified report (delivered in 3-5 business days). Total CFM25, CFM25-O, and a per-register pressure / leakage map (if requested). Format matches your program — IECC, RESNET, ENERGY STAR, NGBS, EarthCraft, FORTIFIED, or your commissioning authority.
Duct Leakage Test pricing (2026 benchmark)
| Project type | 2026 cost |
|---|---|
| Residential standalone duct leakage | $150 – $300 |
| Residential with sealing (if HECS does the sealing) | $250 – $700 |
| Combined blower door + duct leakage | $350 – $650 (saves $50-100 vs. separate visits) |
| Multifamily (per building, 4+ units) | $500+ (per project, quoted on scope) |
| Commercial / light-industrial | $500+ (per project, quoted on scope) |
Pricing is 2026 Midwest benchmark. Travel bundled with related services. Fixed-fee proposal within 24 hours of a free scoping call.
Service area
HECS delivers duct leakage tests across Kentucky, Ohio, Indiana, Tennessee, Illinois, and Missouri. Duct leakage is typically combined with a blower door test on the same visit for the most useful single-visit envelope and distribution diagnostic.
HECS also delivers duct leakage test in:
Duct Leakage Test — frequently asked questions
What is a bad duct leakage number?
Most code-built homes test 5-15% of nominal airflow to outside — that’s 5-15% of your heating/cooling bill going to the attic. A ‘good’ number for ENERGY STAR v3 is CFM25-O ≤5% of nominal airflow. 0% is rare in practice — a perfectly tight duct system on a 2,000 sq ft home still has some leakage at joints.
How long does a duct leakage test take?
About 1-1.5 hours on site for a typical single-family home, including setup, the total test, and the leakage-to-outside test. Combined with a blower door test, plan for 2-3 hours.
Can ducts be tested in winter?
Yes. Duct leakage is pressure-based and not temperature-dependent. HECS runs duct tests year-round, including at temperatures below freezing.
What’s the difference between total CFM25 and CFM25 to outside?
Total CFM25 includes all duct leakage, including leaks inside conditioned space (e.g., a leak in a return duct in the basement of a basement-conditioned home). CFM25-O only counts leakage to unconditioned space — that’s the energy-wasting part.
Can duct leakage be repaired?
Yes. Common fixes include mastic-sealing all duct joints, replacing crushed flex duct runs, and adding returns in under-ducted rooms. HECS provides a sealing service with the test, or delivers a sealed test report if a separate contractor does the sealing.
Do new homes need a duct leakage test for code?
In most jurisdictions, yes. The 2018 and 2021 IECC require a duct leakage test (Section R403.3.3) for code compliance. Some jurisdictions accept a ‘verified’ duct system (with all joints mastic-sealed and verified by visual inspection) in lieu of testing — HECS verifies and tests both.
Related HECS services
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Related HECS services: all HECS services · Contact HECS · HERS Rating · Blower Door Test · Duct Leakage Test · FORTIFIED Roof Evaluation