Duct Leakage Testing Dartmouth MA
RESNET/HERS duct leakage testing in Dartmouth — fast, precise CFM25 results your building department and energy-code file can rely on.
Duct Leakage Requirements in Dartmouth
Dartmouth follows the Massachusetts Stretch Code, which caps total duct leakage at 4 CFM25 per 100 square feet. Our raters measure your ductwork in CFM25 and document a clear pass against the 4 CFM25 per 100 sq ft limit.
| Project / code tier | Duct leakage limit | What is tested |
|---|---|---|
| Base energy code | 4.0 CFM25 / 100 sq ft | Ducts outside conditioned space |
| Stretch Code | 4 CFM25 / 100 sq ft (total) | Total leakage or leakage to outside |
| Specialized Stretch Code | 3.0 CFM25 / 100 sq ft | All ducts, regardless of location |
| Ducts fully inside envelope | Test generally not required | Air handler + ducts in conditioned space |
IECC Duct Leakage Thresholds Reference
Beyond the Massachusetts tier that applies in Dartmouth, these are the federal IECC duct-leakage limits across code editions. All values are CFM at 25 Pascals (CFM25) per 100 sq ft of conditioned floor area (CFA) unless noted.
2009 IECC
| Test stage | Measurement | Leakage limit |
|---|---|---|
| Postconstruction Leakage Test | Duct Leakage to Outdoors | ≤ 8 CFM25 / 100 sq ft CFA |
| Rough-in with AHU | Total Duct Leakage | ≤ 6 CFM25 / 100 sq ft CFA |
| Rough-in without AHU | Total Duct Leakage | ≤ 4 CFM25 / 100 sq ft CFA |
2012, 2015, 2018 & 2021 IECC — Prescriptive Paths
| Test stage | Measurement | Leakage limit |
|---|---|---|
| Postconstruction Leakage Test | Total Duct Leakage | ≤ 4 CFM25 / 100 sq ft CFA |
| Rough-in with AHU | Total Duct Leakage | ≤ 4 CFM25 / 100 sq ft CFA |
| Rough-in without AHU | Total Duct Leakage | ≤ 3 CFM25 / 100 sq ft CFA |
2015 & 2018 IECC — Performance Path (Cost Compliance)
Leakage testing is required unless all ducts and air handlers are located entirely within the thermal envelope. There is no pass/fail threshold for duct leakage on the performance path.
2024 IECC — Prescriptive Path
| Conditioned floor area | Condition at test | Total leakage limit |
|---|---|---|
| >1,000 sq ft CFA | Space-conditioning equipment not installed | < 3 return grilles: ≤ 3 CFM · 3+ return grilles: ≤ 4 CFM |
| >1,000 sq ft CFA | All components installed | < 3 return grilles: ≤ 4 CFM · 3+ return grilles: ≤ 6 CFM |
| >1,000 sq ft CFA | Equipment not installed, ducts entirely in conditioned space | < 3 return grilles: ≤ 6 CFM · 3+ return grilles: ≤ 8 CFM |
| >1,000 sq ft CFA | All components entirely in conditioned space | < 3 return grilles: ≤ 8 CFM · 3+ return grilles: ≤ 12 CFM |
| ≤1,000 sq ft CFA | Equipment not installed | ≤ 30 CFM |
| ≤1,000 sq ft CFA | All components installed | ≤ 40 CFM |
| ≤1,000 sq ft CFA | Equipment not installed, ductwork entirely in conditioned space | ≤ 60 CFM |
| ≤1,000 sq ft CFA | All components entirely in conditioned space | ≤ 80 CFM |
How Duct Leakage Testing Works in Dartmouth
A duct blaster seals off your HVAC system and pressurizes it to 25 Pascals. The airflow needed to hold that pressure is your leakage rate in CFM25 — the lower the number, the tighter the ducts.
Common Sources of Duct Leakage We Check in Dartmouth
Most duct leakage comes from a short list of predictable weak points. Knowing where to look is what turns a CFM25 number into a fixable list of locations.
Boot & register connections
The joint where a duct boot meets the drywall is the single most common leak point — often left unsealed behind the register grille.
Plenum & air-handler seams
Sheet-metal plenums and the cabinet of the air handler leak at seams and access panels unless mastic-sealed.
Disconnected flex runs
Flexible ducts can pull loose at collars or get crushed above insulation, dumping conditioned air into the attic.
Panned-joist returns
Return cavities framed from floor joists or wall studs are notoriously leaky and can draw in unconditioned air.
Building-cavity returns
Using framing cavities as return ducts pulls air from attics, garages, or crawlspaces instead of living space.
Trunk-line joints
Long supply trunks flex and separate at joints over time, especially where they were only taped rather than sealed with mastic.
Why Tight Ducts Keep Heat In Your Dartmouth Home
Ductwork is the delivery system for every dollar of heating and cooling in a Dartmouth home. If it leaks, that conditioned air is lost before it ever reaches a living space.
Once the ducts test tight, the heat you pay for stays in the living space, the system cycles less, and utility bills settle down.
What Your Dartmouth Duct Test Report Includes
You get a document your building department and HERS software will accept the first time — not just a number.
- ✓Leakage normalized per 100 sq ft of conditioned floor area
- ✓Clear pass/fail against the 4.0 CFM25 limit that applies in Dartmouth
- ✓The test method used (rough-in or post-construction) per ANSI/RESNET/ICC 380
- ✓Documentation formatted for your HERS rating and building-permit file
- ✓A punch list of leak locations if a re-seal and retest is needed
- ✓Measured total duct leakage in CFM at 25 Pascals (CFM25)
Best Fit for Projects Like
- Retest visits after sealing failing seams and boots to confirm compliance
- Multi-unit conversions where each system needs documented duct leakage results
- Builders who need a fast, permit-ready duct test scheduled around drywall
- Homes switching to a heat pump where duct tightness protects the new system's output
- Custom homes with complex duct runs that need verification before final inspection
Duct Leakage Testing Dartmouth MA Facts
- Leakage-to-outside testing can be waived under Section 5.5.2 of ANSI/RESNET/ICC 380 when total duct leakage already meets the tighter threshold.
- The Massachusetts Stretch Code requires total duct leakage to stay at or below 4 CFM25 per 100 square feet of conditioned floor area.
- Return-side leaks are especially costly, drawing unconditioned attic or crawlspace air directly into the air handler.
- A documented passing duct test is part of the paperwork many Massachusetts building departments require before final sign-off.
Trusted for Duct Leakage Testing Dartmouth MA
Our Massachusetts Service Locations
Serving clients from our Massachusetts locations in Everett, Somerville, and Framingham.
Everett Location
371 Main St
Everett, MA 02149
Somerville Location
519 Broadway
Somerville, MA 02145
Framingham Location
68 South St
Framingham, MA 01702
Duct Leakage Testing Dartmouth MA FAQ
Get Started With Duct Leakage Testing Dartmouth MA
Fast scheduling and permit-ready CFM25 reports for Dartmouth and all of Bristol County.
Call 617-501-6788
