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 reduces the amount of conditioned air delivered to living spaces, leading to higher energy use and poor airflow distribution throughout the home. As air is lost through the duct system, heating and cooling loads increase, placing added strain on mechanical equipment. Over time, this imbalance can result in uneven temperatures, reduced comfort, and less efficient system operation.
Learn how duct tests work: What Is Duct Leakage Testing?
Duct Leakage in the HERS Rating Model
Within the HERS energy model, measured duct leakage at CFM25 is used to quantify how efficiently conditioned air is delivered throughout the home. This data informs calculations related to HVAC efficiency, distribution losses, and overall energy performance. Because duct leakage directly affects modeled loads and system effectiveness, it also plays a measurable role in the home’s HERS score impact and compliance outcomes.
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