Blower Door Testing Shrewsbury MA
Certified blower door testing in Shrewsbury - 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 Shrewsbury MA
A blower door test is the code-required way to prove how airtight a home in Shrewsbury 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 Shrewsbury
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 Shrewsbury Cold Spells
During a New England cold snap the stack effect goes to work: warm indoor air rises and slips out near the top of the house, and that pulls cold outdoor air in through gaps down low. The colder it gets, the harder this effect pushes - so a leaky home loses the most heat exactly when it can least afford to.
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 Shrewsbury Homes Leak Air
During depressurization the leaks are exaggerated, making them easy to find. In Worcester 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
- Additions over 1,000 sq ft that trigger testing
- New single-family homes needing a code compliance test
- Mass Save incentive and rebate projects
- Drafty existing homes seeking targeted air sealing
Blower Door Testing Shrewsbury MA Facts
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.
Right-sizing equipment
A verified-tight envelope lets a designer right-size the furnace, boiler, or heat pump instead of oversizing for leakage - lowering both equipment cost and running cost.
Comfort, not just code
Beyond passing code, a tight envelope removes drafts, stabilizes room-to-room temperatures, and reduces the dust and outdoor pollen pulled in through gaps.
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.
Trusted for Blower Door Testing Shrewsbury MA
Dominic did an excellent job guiding me through the HERS rating process, and it's clear he genuinely had my best interests in mind.
Knowledgeable and professional. Highly recommend them if you want a thorough efficiency assessment.
When I was going to pull my building permit I was confused about documentation to meet the Massachusetts stretch energy code, but Home Energy was extremely helpful in explaining the HERS rating process and helping me apply for Mass Save rebates.
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 Shrewsbury MA
What documentation do I receive?
You receive the measured ACH50 result on a RESNET/HERS-style report suitable for the building department, plus notes on any sealing performed.
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.
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 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.
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.
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.
Get Started With Blower Door Testing Shrewsbury MA
Book a certified blower door test and get a permit-ready air-tightness report. Call 617-501-6788.
