Blower Door 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.
Blower door requirement in Medford
- New homes in Medford must test at 3.0 ACH50 or tighter under the Massachusetts Stretch Code (Specialized Code town).
- Air-leakage testing is mandatory, measured with a calibrated blower-door fan to the RESNET / ASTM protocol - there is no inspection-only substitute for the result.
- Companion duct leakage limit: 4.0 CFM25 per 100 sq ft of conditioned floor area total leakage (8.0 when all ducts are inside conditioned space - the test is still required).
- Same-day preliminary results; final report in 24-48 hours, filed with the Medford building department.
Mass Save rebates for Medford (2026)
- A tight result unlocks Mass Save all-electric incentives ($7,500 to $25,000 per new single-family home); an all-electric renovation testing at 3.0 ACH50 or better reaches the Level 2 tier, up to $30,000.
- Incentives require a Mass Save-approved, RESNET-certified HERS rater.
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Blower Door Testing Medford MA
Certified blower door testing in Medford - we measure your home's air-tightness in ACH50, pinpoint leaks, and document a passing result for your building permit.
Air-tightness at a glance
Blower Door Testing Medford MA
A blower door test is the code-required way to prove how airtight a home in Medford really is. A calibrated fan depressurizes the house to 50 Pascals so we can measure exactly how much air leaks through the envelope, reported as air changes per hour (ACH50). New construction must reach 3.0 ACH50 or lower, and no home on any compliance path may exceed 5.0 ACH50 (IECC 2021 R402.4.1.2).
| Project type | Max ACH50 | Notes |
|---|---|---|
| New construction | 3.0 or lower | Mandatory blower-door test under R402.4.1.2 |
| Maximum on any compliance path | 5.0 | Code cap under IECC 2021 R402.4.1.2 |
| Addition < 1,000 sq ft | Exempt* | May be exempt from testing (R502.3.1) |
| Passive House (PHI; Phius uses 0.06 CFM50/sq ft) | 0.6 | Whole-building test, Phius/PHI protocol |
*Confirm with your local building department. Requirements per the 2025 MA Stretch Energy Code Technical Guidance.
How Blower Door Testing Works in Medford
The fan mounts in an exterior doorway and holds the home at a fixed 50-Pascal pressure difference - about what a 20 mph wind would exert. The airflow required to maintain that pressure, in CFM, converts to ACH50 using the home's conditioned volume.
The code converts the result to Q50 (CFM at 50 Pa) with Q50 = (Volume × ACH50) ÷ 60. A 2,700 sq ft home at 2 ACH50 works out to roughly 810 CFM50.
Keeping Heat In During Medford Cold Spells
Air-leakage heat loss grows with the gap between indoor and outdoor temperature, which is why a drafty home feels worst in a deep freeze. Warm air you have paid to heat escapes high, cold air rushes in low, and the heating system ends up chasing a load that keeps climbing as the temperature drops.
Sealing and verifying the envelope with a blower door test blunts that stack effect. You keep more of the heat you have already produced, cold-floor drafts fade, and the furnace or heat pump can actually hold temperature through the coldest stretches instead of running flat out and falling behind.
Lower heating load
Less infiltration means a smaller winter heat-loss load and equipment that can keep up.
Retain paid-for heat
Warm air stays in the living space instead of escaping out the top of the house.
Steadier comfort
Fewer cold-floor drafts and a temperature that holds between heating cycles.
Where Medford Homes Leak Air
During depressurization the leaks are exaggerated, making them easy to find. In Middlesex County's older housing stock the usual suspects are rim joists, top plates, attic hatches, recessed lights, and penetrations for plumbing and wiring. Coastal and exposed sites feel wind-driven infiltration most, so a tight, verified envelope pays back quickly here.
Best Fit for Projects Like
- Mass Save incentive and rebate projects
- Additions over 1,000 sq ft that trigger testing
- Pre-drywall diagnostic testing for builders
- New single-family homes needing a code compliance test
- Multi-family and townhouse units
Blower Door Testing Medford MA Facts
Small-addition exemption
Additions under 1,000 sq ft can be exempt from air-leakage testing under R502.3.1, though the connected existing home may still benefit from a test.
Ties into ventilation
Because a tight home needs mechanical fresh air, the verified blower-door rate feeds the R403.6 ventilation sizing under ASHRAE 62.2 - air sealing and ventilation are designed together.
Coastal wind exposure
Homes near the coast face steady wind-driven infiltration, so a tight, well-tested envelope pays back faster in exposed and shoreline locations.
When the test happens
The blower door test is typically run near completion, once the air barrier, windows, and penetrations are sealed but while any needed corrections are still easy to make.
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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
Blower Door Testing in Medford: What to Expect
Medford switched from the Stretch Code to the Specialized (Opt-In) Code on July 1, 2024. The blower door limit for a new home did not change: the result must be 3.0 ACH50 or lower. The Specialized Code adds net-zero-ready requirements, and projects that take the Passive House or Phius route must meet those programs' much tighter limits.
In Medford, inspections go through the inspector
Medford's Building Department is in City Hall, Room 115A, 85 George P. Hassett Drive (781-393-2509), and building applications must be submitted online through CitizenServe. Inspections are made directly with the inspector who issued the permit, during inspector office hours, which start at 8:30 a.m. every weekday. We test at final, before the certificate of occupancy, so have the report in hand when you call.
Older duplexes and multi-family
Medford's Housing Production Plan notes a housing stock with more duplexes and multifamily buildings than Middlesex County or the state as a whole, and reports that 54% of units were built before 1940. In those older two-family and multi-family buildings we focus on rim joists between floors, the top-floor ceiling and attic hatch, recessed lights, and pipe and wire chases. Balloon-framed walls can carry air from the basement to the attic and may need blocking. New single-family homes leak at the same details when the air barrier has gaps.
Before we arrive, and if it fails
Close windows and exterior doors, open interior doors, turn off heating, cooling and ventilation, and fill drain traps with water. We seal exhaust and ventilation openings only as the test protocol allows. If the result is over 3.0 ACH50, we keep the fan running to find the leaks, your crew seals them, and we retest. Our Somerville office at 519 Broadway is the closest HEEC office to Medford.
Real blower door tests by HEEC for Medford projects
These are photos from Home Energy Efficiency Consultants blower door testing jobs in Massachusetts — the same equipment and setup our certified raters bring to Medford homes.
FAQ About Blower Door Testing Medford MA
Do you work with builders and homeowners?
We work with builders, remodelers, designers, and homeowners - from single tests for permit sign-off to pre-drywall diagnostics that catch problems early.
Will sealing my home cause moisture problems?
No - controlled tightness plus proper ventilation actually reduces moisture problems, because you stop humid air from moving through and condensing inside assemblies.
What is a blower door test?
It is a diagnostic that measures how airtight a building is. A calibrated fan mounted in a doorway pressurizes or depressurizes the home to 50 Pascals and measures the airflow needed to hold that pressure, which is reported as ACH50.
What happens if my home fails the test?
The rater locates the leaks with smoke, an infrared camera, or by feel, those areas are sealed, and the home is retested until it meets the target.
How long does a blower door test take?
For a typical single-family home the test itself usually takes well under an hour once the fan is set up and the home is prepared.
Does a tighter house need mechanical ventilation?
Yes. A tight home relies on balanced mechanical ventilation for fresh air, and the code sizes that ventilation (R403.6 / ASHRAE 62.2) using your verified blower-door rate.
Does Medford's Specialized (Opt-In) Code require 2.0 ACH50?
No. Medford has been on the Specialized (Opt-In) Code since July 1, 2024, but the blower door limit for a new home is still 3.0 ACH50 or lower. Only projects that follow the Passive House or Phius path are held to those programs' tighter limits.
How do I schedule a building inspection in Medford?
Medford inspections are scheduled directly with the inspector who issued your permit, during inspector office hours. The Building Department is at City Hall, Room 115A (781-393-2509), and building applications are filed online through CitizenServe.
Blower Door 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.
| Requirement | Limit | Source |
|---|---|---|
| New home, prescriptive path | 3.0 ACH50 or lower | IECC 2021 R402.4.1.3 (Climate Zone 5, all of Massachusetts) |
| Maximum on any compliance path | 5.0 ACH50 or 0.28 CFM50 per sq ft of enclosure | IECC 2021 R402.4.1.2 |
| Attached homes and apartments tested unit by unit | 0.30 CFM50 per sq ft of unit enclosure (alternative) | IECC 2021 R402.4.1.2 exception |
| Mass Save ENERGY STAR tier | 1.5 ACH50 or lower | Mass Save new construction program |
| Passive House (PHI) | 0.6 ACH50 or lower | Passive House Institute |
| Passive House (Phius) | 0.06 CFM50 per sq ft of enclosure (0.08 for non-combustible 5+ stories) | Phius 2024 Certification Guidebook |
How the house is set up for the test
- Exterior windows and doors closed, with no sealing beyond normal weatherstripping
- Dampers closed but not taped, and interior doors open
- Exterior ventilation openings sealed, heating and cooling turned off, supply and return registers open
- Tested at 50 Pascals per ANSI/RESNET/ICC 380, ASTM E779 or ASTM E1827, with a signed report for the Medford building department
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.
Blower Door Questions from Medford Builders
What blower door number does a new home in Medford need?
On the prescriptive path the 2021 IECC requires 3.0 ACH50 or lower in Massachusetts, and no home on any path may exceed 5.0 ACH50. Homes on the HERS path are tested the same way, and the result goes into the HERS model, so a tighter house earns a lower HERS score.
What is ACH50?
Air changes per hour at 50 Pascals: how many times the home's air volume leaks out each hour while a blower door holds the house at 50 Pa. ACH50 = CFM50 × 60 ÷ conditioned volume.
How are townhouses and apartments tested?
Each dwelling unit can be tested on its own and meet 0.30 CFM50 per square foot of the unit's enclosure, which counts walls, floor and ceiling shared with neighbors. Large buildings may also get a whole-building test.
What gets taped or closed during the test?
Windows and exterior doors are closed, dampers are closed but not sealed, and exterior ventilation openings such as bath fan and ERV/HRV terminations are sealed. Interior doors stay open and the heating and cooling system is off.
When should the blower door test happen?
The code test happens at the end of construction. We recommend a pre-drywall test once the air barrier is complete, when leaks are cheap to find and fix, so the final test is a formality.
How much does blower door testing cost in Medford?
Pricing depends on the size of the building and the number of units. Send your plans or address and we will quote the test, or bundle it with your HERS rating and duct test in one visit.
Related: Duct leakage testing in Medford · HERS rating in Medford · Stretch Code help in Medford
Get Started With Blower Door Testing Medford MA
Book a certified blower door test and get a permit-ready air-tightness report. Call 617-501-6788.
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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.
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