Blower Door Testing Medfield MA - Quick Facts
Local energy code in Medfield
- New construction and major renovations in Medfield follow the Massachusetts Stretch Energy Code. IECC Climate Zone 5A.
- Massachusetts has three energy-code levels - base (2021 IECC), Stretch, and Specialized (Opt-In) - and Medfield is on the Stretch Code.
Blower door requirement in Medfield
- New homes in Medfield must test at 3.0 ACH50 or tighter under the Massachusetts Stretch Code.
- 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 Medfield building department.
What you can get back: 2026 Mass Save
- 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.
RESNET-certified · 15,000+ ratings completed · 5.0 stars across 136 Google reviews · (617) 501-6788
Blower Door Testing Medfield MA
Certified blower door testing in Medfield - 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 Medfield MA
A blower door test is the code-required way to prove how airtight a home in Medfield 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 Medfield
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 Medfield Cold Spells
In winter the biggest enemy of a warm home is often invisible air movement. The stack effect drives heated air out through the top of the envelope and draws frigid air in near the floor, robbing heat all season - Cornell extension research describes it plainly as the effect that steals warmth from your home every winter.
A tight, tested envelope shrinks the infiltration share of your heating load. That lets the equipment keep up during cold spells, holds rooms at a steadier temperature between cycles, and often lets a designer right-size the heating system rather than oversizing it to cover leakage.
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 Medfield Homes Leak Air
During depressurization the leaks are exaggerated, making them easy to find. In Norfolk 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
- Custom and high-performance builds
- Mass Save incentive and rebate projects
- Certificate-of-occupancy sign-off
- Multi-family and townhouse units
- Drafty existing homes seeking targeted air sealing
Blower Door Testing Medfield MA Facts
Air leakage and heating cost
Uncontrolled air leakage can raise a home's heating and cooling costs by 30% or more, which is why the code treats envelope tightness as a mandatory measure.
Older housing stock
Much of New England's housing predates modern air-sealing, so existing homes here often start well above 10 ACH50 - leaving large, cost-effective savings on the table.
Warmer floors, fewer drafts
Cutting the cold air drawn in low means warmer floors and fewer cold-corner drafts, which is often the comfort difference people notice first after air sealing.
The ACH50 metric
Results are reported as ACH50 - air changes per hour at 50 Pascals. It tells you how many times per hour the home's entire volume of air would be replaced under that test pressure.
Trusted for Blower Door Testing Medfield MA
One of the most reliable companies that I've worked with in Somerville, Massachusetts.
Very thorough, informative and prompt! Highly recommend!
One of the most reliable HERS rating companies I have dealt with in Massachusetts.
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
Real blower door tests by HEEC for Medfield 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 Medfield homes.
FAQ About Blower Door Testing Medfield MA
What ACH50 does new construction need to pass?
New residential construction in Massachusetts must measure 3.0 ACH50 or lower. Many high-performance homes come in well below that figure.
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.
Do additions need a blower door test?
Many do, but additions under 1,000 square feet can be exempt from air-leakage testing under R502.3.1. We can confirm what your specific project requires.
Can a blower door test find where my home is drafty?
Yes. Depressurizing the home exaggerates the leaks so a rater can pinpoint exactly where outdoor air is entering, which guides targeted air sealing.
Will a tighter home lower my heating load?
Yes. Infiltration is one of the largest parts of a winter heat-loss calculation. Reducing leakage directly shrinks the heating load, which can mean right-sized equipment, lower bills, and a home that holds temperature better in cold weather.
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.
Blower Door Test Requirements for Medfield Projects
Medfield is not on the Specialized Code list, so new homes follow the Massachusetts Stretch Code (225 CMR 22.00), adopted by 242 communities, or the base code if Medfield has not adopted it. The testing requirements below come from 225 CMR 22.00 and the 2021 IECC it amends.
| 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 Medfield building department
Sources: 225 CMR 22.00 (2025 edition) and the 2021 IECC sections listed. Medfield is in Norfolk County, served from our Framingham (68 South St) office.
Blower Door Questions from Medfield Builders
What blower door number does a new home in Medfield 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 Medfield?
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 Medfield · HERS rating in Medfield · Stretch Code help in Medfield
Get Started With Blower Door Testing Medfield MA
Book a certified blower door test and get a permit-ready air-tightness report. Call 617-501-6788.
Mass Save®-Listed HERS Rater
U.S. DOE Efficient New HomeTrusted Partner — Verified
ENERGY STAR®Partner
Phius CertifiedPassive House Verifier
ICCMember★★★★★136 Google
Reviews
The Phius Certified Verifier logo is used under license from Phius.
HERS Ratings in Medfield, Massachusetts
Home Energy Efficiency Consultants provides Medfield with certified HERS ratings, blower door and duct leakage testing, and Massachusetts energy-code compliance for new construction, additions, and major renovations — with same-day preliminary reports.
We rate homes across the Commonwealth from our four offices. Reach the one nearest your Medfield project — Somerville, Framingham, Marlborough, or Everett — or call (617) 501-6788 to schedule a Medfield rating.
More Massachusetts Towns We Serve
Certified HERS ratings, blower door testing and energy code compliance across all 351 Massachusetts cities and towns.
