HERS Rating for Accessory Dwelling Units (ADUs) in Massachusetts

Stretch Energy Code Compliance & Mass Save® Rebate Support

If you are building an Accessory Dwelling Unit (ADU) in Massachusetts, a HERS Rating is often required to meet the state’s energy code and qualify for valuable rebates. Our company provides complete HERS Rating services for ADUs across Massachusetts, including energy modeling, code compliance documentation, blower door testing, duct testing, and Mass Save® rebate coordination.

Whether your ADU is detached, attached, over a garage, or part of a basement conversion, we help you meet the latest energy requirements efficiently and cost-effectively.

What Is a HERS Rating?

A HERS (Home Energy Rating System) Rating is a nationally recognized energy performance score that measures a home’s efficiency. The lower the score, the more energy efficient the home.

In Massachusetts, HERS Ratings are commonly required to comply with:

• The Massachusetts Stretch Energy Code

• The International Energy Conservation Code (IECC 2021 base code)

• Local municipal adoption of high-performance energy standards

For many ADU projects, especially in Stretch Code communities, a certified HERS Rater must model and verify that the dwelling meets the required performance target.

Why HERS Ratings Are Important for ADUs in Massachusetts

ADUs are growing rapidly across Massachusetts due to housing demand and zoning updates. However, they must still meet strict energy efficiency standards.

A HERS Rating ensures your ADU:

✔ Meets Stretch Energy Code performance targets
✔ Passes required blower door testing
✔ Passes duct leakage testing (if applicable)
✔ Qualifies for Mass Save® rebates
✔ Avoids costly delays at final inspection
✔ Is designed for long-term energy savings

Because ADUs are typically smaller structures, energy modeling becomes even more critical. Proper insulation design, HVAC sizing, ventilation systems (ERV/HRV), and window performance all directly affect your HERS score.

Our 3-Phase HERS Rating Process for ADUs

Phase 1: Plan Review & Energy Modeling

We begin by creating a custom energy model of your ADU using accredited HERS software. This modeling evaluates:

• Building envelope performance

• Insulation values

• Window U-factor & SHGC

• Air sealing strategy

• Heating & cooling systems

• Water heating systems

• Ventilation design

You receive a Preliminary HERS Report, which is often required for permit approval in Massachusetts Stretch Code communities.

Phase 2: Insulation Inspection & Energy Consulting

Before drywall installation, we conduct a required insulation inspection to verify:

• Proper insulation installation

• Thermal bypass sealing

• Air barrier continuity

• Foundation or attic insulation strategy

We also provide real-time consulting to ensure the project stays on track to meet the final HERS target.

Phase 3: Final Testing & Certification

Once construction is complete, we perform:

• Blower door testing (air leakage verification)

• Duct leakage testing (if ducted systems are installed)

• Mechanical system verification

• Equipment serial number documentation

After passing, we issue the Final HERS Certificate required for occupancy.

Massachusetts Stretch Energy Code & ADUs

The Massachusetts Stretch Energy Code requires performance-based compliance in most municipalities throughout the state.

For ADUs, compliance may include:

• Meeting a target HERS Index score

• Achieving strict air leakage limits (ACH50 targets)

• High-efficiency heat pump systems

• Energy recovery ventilation (ERV)

• Enhanced insulation levels

Many towns require the preliminary HERS report before issuing building permits and the final certificate before granting occupancy.

Mass Save® Rebates for ADUs

Through the Mass Save program, ADU projects may qualify for substantial rebates — especially if designed as all-electric, high-efficiency homes.

Potential incentives may include:

• Whole-home performance rebates

• Heat pump incentives

• Heat pump water heater rebates

• Enhanced insulation rebates

• All-electric bonus incentives

Proper HERS documentation is essential to secure these rebates. We coordinate the rebate process and ensure your equipment meets program requirements.

All-Electric ADUs: Maximizing Efficiency & Rebates

Designing your ADU as all-electric with high-efficiency heat pumps often:

• Improves your HERS score

• Simplifies compliance

• Increases rebate eligibility

• Reduces long-term utility costs

We help evaluate whether all-electric or mixed-fuel design makes the most financial sense for your project.

Why Choose a Certified HERS Rating Specialist?

Choosing an experienced Massachusetts HERS Rater helps:

• Prevent redesign costs

• Avoid failed inspections

• Maintain construction timelines

• Maximize rebate returns

• Keep projects compliant statewide

We work with homeowners, builders, and developers across Massachusetts and understand local building department expectations.

Frequently Asked Questions (FAQ)

Is a HERS Rating required for all ADUs in Massachusetts?

In most Stretch Code municipalities, yes. A performance pathway requires HERS modeling and field verification.

When is the HERS Rating started?

Immediately after receiving architectural plans, before permit submission.

Do ADUs qualify for Mass Save rebates?

Yes, many do — especially all-electric ADUs meeting performance standards.

What tests are required?

Blower door testing is required. Duct testing is required if ducts are outside conditioned space.

How long does the process take?

Preliminary reports are typically completed quickly after receiving final plans. Final certification occurs after passing testing.

Get Started with Your Massachusetts ADU HERS Rating

If you are building an Accessory Dwelling Unit in Massachusetts, we provide start-to-finish HERS Rating services including:

• Energy modeling

• Stretch Code compliance

• Insulation inspections

• Blower door testing

• Duct testing

• Mass Save rebate coordination

Contact us today to begin your ADU HERS Rating and ensure your project meets Massachusetts energy code requirements while maximizing available incentives.