Blower Door Testing Cohasset MA - Quick Facts
Local energy code in Cohasset
- Cohasset enforces the Massachusetts Stretch Energy Code for new construction and major renovations. IECC Climate Zone 5A.
- Massachusetts has three energy-code levels - base (2021 IECC), Stretch, and Specialized (Opt-In) - and Cohasset is on the Stretch Code.
Blower door requirement in Cohasset
- New homes in Cohasset 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 CFM25 per 100 sq ft of conditioned floor area when ducts run outside conditioned space.
- Same-day preliminary results; final report in 24-48 hours, filed with the Cohasset building department.
2026 Mass Save incentives in Cohasset
- 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 135 Google reviews · (617) 501-6788
Blower Door Testing Cohasset MA
Certified blower door testing in Cohasset - 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 Cohasset MA
A blower door test is the code-required way to prove how airtight a home in Cohasset 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, while remodels are allowed up to 5.0 ACH50.
| Project type | Max ACH50 | Notes |
|---|---|---|
| New construction | 3.0 or lower | Mandatory blower-door test under R402.4.1.2 |
| Remodel / alteration | 5.0 | Realistic target for existing assemblies |
| Addition < 1,000 sq ft | Exempt* | May be exempt from testing (R502.3.1) |
| Passive House / Specialized | 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 Cohasset
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 Cohasset 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.
Once the leaks are found and sealed, the home retains heat far longer between heating cycles. Floors stay warmer, temperatures hold steady on windy nights, and the reduced heating load shows up directly on winter utility bills.
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 Cohasset 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
- Multi-family and townhouse units
- New single-family homes needing a code compliance test
- Pre-drywall diagnostic testing for builders
- Certificate-of-occupancy sign-off
- Homes chasing Passive House or net-zero targets
Blower Door Testing Cohasset MA Facts
Infiltration and heat load
Infiltration is frequently the single largest line item in a residential heat-loss calculation, so a tighter envelope directly shrinks the required heating capacity.
Documentation for permits
Passing results are recorded on a RESNET/HERS-style form that becomes part of the building permit and certificate of occupancy file.
Steadier indoor temperature
A tight home holds its heat longer between heating cycles, so rooms stay at a steadier temperature and recover faster after a cold, windy night.
The reference scale
For perspective, a very leaky older home can exceed 11 ACH50, current code sits at 3.0 for new builds, and certified Passive House projects reach 0.2 to 0.6 ACH50.
Trusted for Blower Door Testing Cohasset MA
I worked with this HERS rating company in South Boston on a remodel project and was able to get back 30,000 in rebates.
I am building a 5-unit conversion in East Boston and used this HERS rating company. Some of the most reasonable, knowledgeable HERS raters I have dealt with in the greater Boston area.
One of the most reliable companies that I've worked with in Somerville, 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
FAQ About Blower Door Testing Cohasset 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.
How is ACH50 converted to CFM?
The code uses Q50 = (conditioned volume x ACH50) / 60. For example, a 2,700 sq ft home with 9 ft ceilings at 2 ACH50 equals about 810 CFM50.
What does the 50 Pascal test pressure represent?
Fifty Pascals is roughly the pressure a 20 mph wind exerts on the whole building. Testing at a fixed pressure makes the result repeatable regardless of the weather that day.
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.
How tight is a Passive House?
Passive House projects on the Specialized Code path target around 0.6 ACH50 - roughly ten times tighter than base code - verified with a whole-building blower-door test.
Is a blower door test required by code?
Yes. Air-leakage testing is mandatory under R402.4.1.2 for new residential construction, verified with a blower door at 50 Pascals.
Get Started With Blower Door Testing Cohasset MA
Book a certified blower door test and get a permit-ready air-tightness report. Call 617-501-6788.
HERS Ratings in Cohasset, Massachusetts
Home Energy Efficiency Consultants provides Cohasset 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 Cohasset project — Somerville, Framingham, Marlborough, or Everett — or call (617) 501-6788 to schedule a Cohasset rating.
More Massachusetts Towns We Serve
Certified HERS ratings, blower door testing and energy code compliance across all 351 Massachusetts cities and towns.
