Duct leakage is one of the key variables affecting a home’s HERS Score. Leaky ducts reduce heating and cooling efficiency, increase system runtime, and cause comfort issues — especially in cold climates like Massachusetts and Rhode Island.
Because duct systems must deliver air efficiently to each space, leakage values feed directly into your HERS model.
How Duct Leakage Affects Efficiency
Excess duct leakage leads to:
- Higher energy use
- Poor airflow distribution
- Increased heating/cooling load
- Mechanical system strain
- Temperature imbalances
Learn how duct tests work:
What Is Duct Leakage Testing?
Duct Leakage in the HERS Rating Model
The HERS energy model uses CFM25 duct leakage data to calculate:
- HVAC efficiency
- Distribution losses
- Overall energy performance
- HERS Score impact
Learn how scoring works:
Understanding Your HERS Score
Required Leakage Levels in MA & RI
Massachusetts
- Ducts outside conditioned space must meet CFM25 thresholds
- Required under MA 780 CMR & Stretch Code
Rhode Island
- Duct leakage testing required under RI IECC 20241
- Typically ≤ 4 CFM25 per 100 sq. ft.
More details:
Duct Testing for Code Compliance
Improving Duct Leakage Before Testing
Energy Geeks may recommend:
- Sealing joints and connections
- Tightening mechanical room penetrations
- Insulating attic/garage duct runs
- Using mastic or UL-rated foil tape
Learn what to expect during testing:
Duct Testing – What to Expect
