Duct Leakage Testing Medford MA - Quick Facts
Local energy code in Medford
- As of July 1, 2024, Medford enforces the Massachusetts Specialized (Opt-In) Energy Code on top of the Stretch Code baseline - IECC Climate Zone 5A.
- The Opt-In code goes further than the Stretch baseline: new fossil-fuel homes must be pre-wired for electrification and include on-site solar where roof space allows.
- New all-electric homes rely on heat pumps for heat and hot water; large fossil-fuel homes over 4,000 sq ft must hit net-zero (HERS 0), and multifamily over 12,000 sq ft must be Passive House.
Duct leakage requirement in Medford
- Medford permits under the Massachusetts Stretch Code cap duct leakage at 4 CFM25 per 100 sq ft of conditioned floor area.
- Testing is required unless the entire duct system and air handler sit inside conditioned space; a rough-in test and a final test may both apply.
- Results in 24-48 hours with clear pass/fail documentation, filed with the Medford building department.
- From $350 for the first ducted system, often bundled with blower door testing and a full HERS rating.
Mass Save rebates for Medford (2026)
- Duct and blower door results feed the HERS rating that unlocks Mass Save all-electric incentives: $7,500 to $25,000 per new single-family home and $1,000 to $3,750 per multifamily unit.
- Incentives require a Mass Save-approved, RESNET-certified HERS rater.
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Duct Leakage Testing Medford MA
RESNET/HERS duct leakage testing in Medford — fast, precise CFM25 results your building department and energy-code file can rely on.
Duct Leakage Requirements in Medford
Medford enforces the Massachusetts Specialized (Opt-In) Code, which uses the same duct leakage limit as the Stretch Code: 4.0 CFM25 per 100 square feet of total leakage, or 3.0 at rough-in before the air handler is installed. Our raters measure your ductwork in CFM25 and document a clear pass against the 4.0 CFM25 per 100 sq ft limit.
| Project / code tier | Duct leakage limit | What is tested |
|---|---|---|
| Base energy code | 4.0 CFM25 / 100 sq ft | Total leakage (every ducted system) |
| Stretch Code | 4 CFM25 / 100 sq ft (total) | Total leakage (leakage to outside is not a code option) |
| Rough-in test, air handler not installed | 3.0 CFM25 / 100 sq ft | Total leakage (Stretch and Specialized) |
| Ducts fully inside envelope | 8.0 CFM25 / 100 sq ft (test still required) | Air handler + ducts in conditioned space |
IECC Duct Leakage Thresholds Reference
Beyond the Massachusetts tier that applies in Medford, 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 Medford
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 Medford
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 Medford Home
Ductwork is the delivery system for every dollar of heating and cooling in a Medford home. If it leaks, that conditioned air is lost before it ever reaches a living space.
A verified-tight duct system means a right-sized furnace or heat pump can deliver its full output where it's needed, steadying comfort and cutting waste.
What Your Medford 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 Medford
- ✓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
- Medford new-construction homes needing a duct test to complete the HERS rating
- Homes switching to a heat pump where duct tightness protects the new system's output
- Rough-in duct tests before the air handler is set, which must hit 3.0 CFM25 per 100 sq ft
- Multi-unit conversions where each system needs documented duct leakage results
- Homeowners chasing comfort fixes for hot-and-cold rooms caused by duct leaks
Duct Leakage Testing Medford MA Facts
- A duct leakage tester, or duct blaster, pairs a calibrated fan with a precise pressure sensor to quantify how leaky the ducts are.
- The U.S. Department of Energy estimates a typical home loses 20 to 30 percent of its conditioned air through duct leaks.
- The 2025 Massachusetts Technical Guidance requires HVAC ducts newly installed as part of an addition to comply with Section R403.
- Test results are reported as CFM25 and normalized per 100 square feet so any home can be compared to the code limit.
Trusted for Duct Leakage Testing Medford 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 for Medford Homes
Medford adopted the Specialized (Opt-In) Code effective July 1, 2024, after more than a decade on the Stretch Code. Some online summaries still describe Medford as a Stretch Code city, but the state's adoption list shows the change. For duct testing the requirement is identical under both: every ducted system gets a total duct leakage test, and it must measure 4.0 CFM25 or less per 100 sq ft of conditioned floor area. With all ducts and the air handler inside conditioned space the limit is 8.0, and the test is still required.
A city of two-family houses
Medford's Housing Production Plan describes the city's stock of two-unit houses as one of its defining features: about 27 percent of residential structures are two-unit buildings, and 54 percent of housing units were built before 1940. In a two-family, new ductwork for the upper unit usually runs through the attic and the first-floor system along the basement ceiling, each with its own air handler.
That layout gives us a clear checklist:
- boot-to-drywall gaps at every ceiling and floor register
- flex duct connections in the attic, which get crushed or pulled loose
- air handler cabinet seams and access panels
- trunk takeoffs along the basement ceiling
Testing each system
Two units usually means two systems and two tests. A rough-in test on each catches leaks while the ceilings are open; the final test confirms each finished system. Tight ducts let a ducted heat pump deliver its rated airflow and lower the HERS score that a Specialized Code home is measured against.
The Medford Building Department is in City Hall, Room 115A, 85 George P. Hassett Drive, (781) 393-2509. Building applications are submitted online through Citizenserve, and the city asks you to contact the inspector who issued the permit during office hours. National Grid supplies electricity and gas. We serve Medford from our Somerville office at 519 Broadway.
Real duct leakage tests by HEEC for Medford projects
These are photos from Home Energy Efficiency Consultants duct leakage testing jobs in Massachusetts — the same equipment and setup our certified raters bring to Medford homes.
Duct Leakage Testing Medford MA FAQ
Duct Leakage Test Requirements for Medford Projects
Medford is one of the 60 Massachusetts communities on the Specialized (Opt-In) Code. New homes there are built on the same 225 CMR 22.00 testing requirements below, plus net-zero-ready provisions.
| Test | Limit (CFM25 per 100 sq ft of conditioned floor area) | Notes |
|---|---|---|
| Rough-in, air handler installed | 4.0 total leakage | ANSI/RESNET/ICC 380 or ASTM E1554 |
| Rough-in, air handler not installed | 3.0 total leakage | Air handler added later |
| Post-construction | 4.0 total leakage | Final test with the system complete |
| Ducts and air handler entirely inside the thermal envelope | 8.0 total leakage | Test is still required |
| Ventilation-only ducts | Exempt | Only if not tied into heating or cooling ducts |
Massachusetts measures total duct leakage; "leakage to outside" is not a code option. Under the Massachusetts amendment to R403.3.5, the test must be done by a HERS Rater, HERS Rating Field Inspector or BPI Certified Professional, with a signed report to the Medford building department. Mechanical ventilation airflow must also be tested and verified by a HERS Rater under R403.6.3.
Sources: 225 CMR 22.00 (2025 edition) and the 2021 IECC sections listed. Medford is in Middlesex County, served from our Somerville (519 Broadway) office.
Duct Leakage Questions from Medford Builders
What is the duct leakage limit for a new home in Medford?
4.0 CFM25 of total leakage per 100 square feet of conditioned floor area, at rough-in or after construction. If the air handler is not installed at rough-in the limit is 3.0, and if every duct and the air handler are inside the thermal envelope the limit is 8.0.
Can leakage to outside be used instead of total leakage?
No. The Massachusetts code (225 CMR 22.00 R403.3.5) measures total duct leakage. Leakage-to-outside tests are used by some programs, but not for code compliance here.
Who can perform the duct test in Massachusetts?
A HERS Rater, a HERS Rating Field Inspector or a BPI Certified Professional, under the Massachusetts amendment to R403.3.5. The tester signs a written report for the code official.
Is a duct test required if all ducts are inside conditioned space?
Yes. Massachusetts follows the 2021 IECC, which still requires the test but allows up to 8.0 CFM25 per 100 square feet when the ducts and air handler are entirely inside the thermal envelope.
Rough-in or final: which test is better?
A rough-in test catches leaks while every joint is still reachable, so fixes are cheap. A post-construction test confirms the finished system. Many builders do both to avoid surprises at final.
How much does duct leakage testing cost in Medford?
Our duct testing is $350 for the first ducted system and $250 for each additional system at the same address. It can be done in the same visit as the blower door test and HERS inspection.
Related: Blower door testing in Medford · HERS rating in Medford · Stretch Code help in Medford
Get Started With Duct Leakage Testing Medford MA
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HERS Ratings Across Medford and Nearby Communities
Home Energy Efficiency Consultants rates new homes, additions, and major renovations throughout Medford — from West Medford, Medford Square, and Wellington to South Medford and Glenwood. Every Medford project is filed with the City of Medford Building Department, and we handle the energy model, blower door and duct leakage testing, and the compliance paperwork from start to finish.
We also serve the communities right around Medford, including Somerville, Malden, Arlington, Winchester, and Everett. Our Somerville office at 519 Broadway is the closest of our four Massachusetts locations — see our Somerville office or call (617) 501-6788 to get a Medford rating on the schedule.
Medford Specialized Energy Code — HERS Index Targets
Medford enforces the Massachusetts Specialized (Opt-In) Energy Code. The required HERS score depends on fuel type and project scope — a lower index is stricter.
| Project type | Mixed-fuel | Mixed-fuel + solar | All-electric | All-electric + solar |
|---|---|---|---|---|
| New construction | HERS 42 | 42 | 45 | 45 |
| New construction — embodied-carbon credit | 45 | 45 | 48 | 48 |
| Accessory dwelling unit (ADU) | 52 | 55 | 55 | 58 |
| Major alteration / renovation / change of use | 65 | 70 | 70 | 75 |
A HERS rating is triggered by new construction, additions over 1,000 sq ft (or more than 100% of the existing conditioned area), and Level 3 alterations over 1,000 sq ft affecting more than 50% of the home. New homes must also pass a blower-door test at 3.0 ACH50 and include electrification-ready wiring for heat pumps, EV charging, and solar. We model your Medford project up front so you know the exact target and the fastest path to hit it — call (617) 501-6788.
