Published: May 2026 | Duct LeakageMassachusettsEnergy Testing
Duct leakage testing is a required component of HERS Ratings and MA Stretch Code compliance in Massachusetts — but many builders don’t fully understand what’s being tested or how to ensure their duct systems pass.
What Is Duct Leakage Testing?
Duct leakage testing uses a device called a duct blaster to measure how much conditioned air escapes from the duct system before reaching living spaces. The duct blaster pressurizes the duct system to 25 pascals and measures the airflow required to maintain that pressure — revealing how much air is leaking.
Why Does Duct Leakage Matter?
Leaky ducts can waste 20–30% of a home’s conditioned air. In Massachusetts’s climate, this means heating and cooling systems work significantly harder, driving up energy bills and reducing comfort. For new construction, duct leakage above specified limits fails both HERS requirements and MA Stretch Code compliance.
When Is Duct Leakage Testing Required?
- All HERS Ratings: Duct leakage testing is required for every HERS Rating in Massachusetts, regardless of Stretch Code adoption status.
- MA Stretch Code compliance: Required in all 300+ municipalities that have adopted the Stretch Code.
- Mass Save new construction programs: Required to document duct performance for incentive programs.
What Are the Duct Leakage Limits?
Under the MA Stretch Code and HERS Rating standards, duct systems must meet specific leakage limits measured in CFM25 (cubic feet per minute at 25 pascals). Your HERS Rater will calculate the allowable leakage based on your home’s conditioned floor area and verify compliance through testing.
Tips to Pass Duct Leakage Testing
- Seal all supply and return duct connections with mastic sealant — not just duct tape.
- Seal around air handler cabinet seams and access panels.
- Insulate and seal duct boots where they connect to the floor, wall, or ceiling.
- Have your HVAC contractor pressure-test the duct system before the HERS inspection.
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