The Builder Who Couldn’t Pass His Blower Door Test

A builder in Worcester called and said, “We failed our Energy Star inspection twice — the house keeps leaking air somewhere, and we can’t find it.”
He’d used fiberglass batts in the walls and attic, thinking it would be enough. The problem wasn’t the amount of insulation — it was the air leakage.

We sprayed closed-cell foam on the rim joists, attic deck, and around penetrations. The house passed the next test with flying colors.
He texted after: “Inspector said it was the tightest house he’s tested all month.”

That’s the difference spray foam makes — it’s not just insulation, it’s an air-sealing system that helps builders and homeowners hit Energy Star and HERS targets easily.

What Energy Star and HERS Ratings Actually Mean

Let’s keep it simple.
Energy Star Homes are built or renovated to meet strict U.S. EPA standards for energy efficiency — lower air leakage, controlled ventilation, and strong thermal performance.

The HERS Index (Home Energy Rating System) is like a “miles per gallon” score for homes.
Lower score = better efficiency.
A typical code-built house scores around 100.
Energy Star homes usually score 85 or below.
Spray foam-insulated homes often hit 60–70, or even lower.

So when you hear about Energy Star or HERS, it’s really about one thing: how well your home keeps heated or cooled air inside.

Why Spray Foam Excels Where Fiberglass Falls Short

Traditional insulation slows heat flow but doesn’t stop air movement.
Air leaks through outlets, gaps, rim joists, attics, and plumbing chases — and those leaks kill energy scores.

Spray foam does both:

1. Insulates — high R-value per inch.

2. Air-seals — expands and bonds to framing, stopping leaks completely.

When used properly, it cuts air infiltration by up to 70%, which directly boosts HERS ratings and Energy Star compliance.

Real Story: The Shrewsbury Duplex

A contractor building two side-by-side units told us, “We need a tighter envelope or we won’t qualify for rebates.”
We insulated the roof deck and rim joists with closed-cell foam, then used open-cell foam in the interior partitions for sound control.

After testing, the HERS score dropped from 92 to 67.
They earned their Energy Star certification — and a rebate from Mass Save.
The builder said, “I’m using spray foam on every project from now on.”

How Spray Foam Directly Improves HERS Ratings

HERS raters measure five big areas:

1. Air leakage (blower door test)

2. Insulation quality and R-value

3. Duct leakage

4. Window and door performance

5. HVAC efficiency

Spray foam impacts the first two the most — and indirectly helps the rest.

When the building envelope is sealed:

• HVAC systems can be smaller.

• Ducts lose less energy.

• Interior temps stay consistent.

That combination sends your HERS score plummeting (in a good way).

The Power of R-Value per Inch

Closed-cell foam offers nearly double the insulation power of fiberglass and acts as a vapor barrier.
That’s why new Energy Star homes across Massachusetts use it in walls, attics, and rim joists.

Energy Star Requirements Made Simple

To meet Energy Star v3/v3.1 standards in Massachusetts, builders must achieve:

• ≤ 3 ACH50 (air changes per hour) on blower door test

• Proper R-values per climate zone (Zone 5 here)

• Verified insulation installation quality (Grade 1)

• Complete air barrier alignment

Spray foam simplifies all that — because one product satisfies air barrier + insulation + vapor control.

Instead of chasing leaks with tape and caulk, foam does it all in one spray.

Real Story: The Westborough Remodel

A remodeling contractor said, “We’re upgrading an old colonial to Energy Star specs — can spray foam help us hit the target?”

We sprayed the roof deck and exterior walls with closed-cell foam, sealed the attic hatch, and foamed around can lights.

The house scored HERS 63 on the final test — beating the Energy Star goal by 15 points.
The rater wrote on his report: “Exceptional air sealing results.”

It’s always satisfying when a project passes on the first try.

Where Spray Foam Makes the Biggest Difference

• Rim joists – major air leakage point in New England homes.

• Attics & roof decks – stops stack effect and ice dams.

• Basements – controls moisture, improves comfort upstairs.

• Wall cavities – perfect for new construction or gut remodels.

• Knee walls / cathedral ceilings – eliminates tricky thermal bridging.

Energy Star compliance is easier when every hidden gap is sealed.

The “Stack Effect” Problem

In cold Worcester winters, warm air rises and escapes through the attic.
That creates negative pressure that sucks cold air in through the basement or crawl space — the “stack effect.”

Fiberglass can’t stop it. Spray foam can.
By sealing both top and bottom, you balance the pressure and keep the warm air inside where it belongs.

This single fix can drop a blower-door score by 1–1.5 ACH.

Moisture and Mold Resistance

Energy Star inspectors also check for moisture management.
Closed-cell spray foam acts as a vapor retarder — preventing condensation on cold surfaces.

No condensation = no mold = a healthier indoor environment.
That helps homes meet Indoor airPLUS standards, which pair with Energy Star certification.

Comfort and Quiet

A HERS score measures efficiency, but comfort sells the job.
Open-cell foam absorbs sound between rooms, while closed-cell foam stiffens framing — eliminating rattles and drafts.

Builders love that they can deliver quiet, solid-feeling homes that also test well.

HVAC Right-Sizing and Equipment Longevity

When a home is tightly sealed, HVAC load drops dramatically.
That means smaller systems, less runtime, and longer lifespan.

HERS raters adjust scores based on HVAC size vs. actual load.
Spray foam helps you downsize equipment and boost the rating even further.

It’s not uncommon for builders to cut HVAC tonnage by 30–40% once spray foam is installed.

Energy Savings and Rebates

Homes that achieve low HERS scores often qualify for Mass Save new-construction incentives.
Builders and homeowners can earn:

• Rebates per kWh saved

• Free duct testing

• Lower mortgage rates on Energy Star Certified Homes

One Worcester builder saved nearly $2,000 in rebate value per home by hitting the energy targets.

Real Story: The Sutton Ranch

This builder used spray foam in the roof deck and exterior walls.
The rater’s report came back: ACH50 = 2.3 (well below code).

They hit HERS 59, far better than average.
The homeowner later said, “We barely hear the furnace run — it’s quiet and comfortable all year.”

That’s efficiency you can feel, not just measure.

Environmental Impact

Closed-cell foams now use low-GWP (Global Warming Potential) blowing agents — far better for the environment.
A sealed, efficient home can reduce CO₂ emissions by 2–3 tons per year, just from less fuel use.

So beyond ratings, spray foam helps Massachusetts move toward its energy-efficiency goals.

Common Myths About Spray Foam & Energy Ratings

Myth #1: “It’s overkill for small homes.”
➡️ Even a small Worcester ranch can lose 25% of heat through air leaks. Foam pays off quickly.

Myth #2: “Inspectors don’t allow it without drywall.”
➡️ True only if exposed — we add fire-rated coatings like DC315 to meet code.

Myth #3: “It traps moisture.”
➡️ Not when applied correctly — closed-cell foam prevents moisture by stopping air infiltration.

Typical HERS Results with Spray Foam

Each 1-point drop on the HERS scale = 1% improvement in energy efficiency.

Builder Tips for Passing Energy Star Tests with Spray Foam

1. Seal rim joists first — biggest leak zone.

2. Don’t forget attic hatches and can lights.

3. Apply consistent foam thickness (inspect visually).

4. Pair foam with a thermal barrier coating.

5. Test early — before drywall — to fix leaks fast.

Following those five steps almost guarantees a passing score.

For Homeowners

If you’re building or remodeling, ask your contractor if they’re using spray foam for energy compliance.
It’s not just about bills — it’s about comfort, health, and long-term performance.

You’ll get a quieter, drier, more consistent home that keeps value for decades.

For Builders and General Contractors

If you’re tired of blower-door fails or insulation callbacks, switch to spray foam.
You’ll meet Energy Star and HERS targets faster and get fewer warranty headaches.

We work with GCs all over Central MA who now make foam their standard spec.
One said, “It just works — and inspectors love the numbers.”

Before and After

Before: Failing blower-door, uneven temps, cold walls.
After: Tight envelope, consistent comfort, certified Energy Star.

It’s not marketing — it’s physics.
Seal the leaks, control the air, and everything else improves.

Final Thoughts

Spray foam isn’t just an upgrade — it’s the shortcut to hitting Energy Star and HERS goals in Massachusetts homes.
It seals what others miss, boosts R-value, and delivers a comfort level homeowners instantly notice.

Whether you’re a homeowner building a dream house or a GC aiming for a 60 HERS score, spray foam is your simplest path to passing.

Call your local insulation contractor in Worcester today for a free evaluation or builder consultation.
We’ll help you hit your rating target — and make every project a little warmer, tighter, and smarter.