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Duct Leakage Test and Operating Loss Calculator

Normalize comparable duct pressure-test records or model sensible transfer and electric cost using separately supported operating leakage assumptions.

Use this result well

Inputs that matter
Before test leakage (CFM), After test leakage (CFM), Served floor area (ft²), Common test pressure magnitude (Pa), and 8 more
Output to expect
Duct leakage test comparison, Operating leakage sensible-energy scenario
  • Check the units and required inputs before comparing results.
  • Keep the assumptions with a copied result so you can reproduce the calculation later.
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Reference & details

How it works

Duct leakage test comparison

Normalize two documented duct-leakage test readings by the same served floor area and compare the readings. Keep total leakage and leakage to outdoors separate, and use the same test pressure, configuration and method for both records.

Normalized leakage = test CFM × 100 ÷ served floor area; change = after − before test CFM.

Operating leakage sensible-energy scenario

Model a documented operating leakage flow and relevant air-to-surroundings temperature difference. The electric-input equivalent also requires explicit operating hours and a compatible effective COP. Do not enter CFM25 from a pressurized duct test as operating airflow.

Sensible transfer Btu/h = operating leakage CFM × air coefficient × ΔT; electric kWh equivalent = Btu/h × hours ÷ (3412.141633 × COP).

Updated: September 2026

Example Scenarios

The built-in example is an arithmetic illustration. Replace it with your own verified measurements or planning assumptions.

→ 4 CFM/100 ft² at 25 Pa

The built-in example is an arithmetic illustration. Replace it with your own verified measurements or planning assumptions.

→ 2,160 Btu/h sensible transfer

FAQ

No. Test leakage at a stated pressure is not normal operating leakage. The separate operating scenario needs a supported flow, temperature difference, coefficient, hours, effective electric COP and tariff.

Use the actual source documents, units and operating conditions shown in the selected mode. Replace illustrative examples with your records, enter explicit zeros only where valid and retain unresolved assumptions.

Choose Save planning case for local history. Copy MD retains current inputs, notes and interpretation; Download CSV exports the result breakdown. Export a separate copy before changing devices or clearing browser storage.

About Duct Leakage Test and Operating Loss Calculator

Normalize two documented duct-leakage test readings by the same served floor area and compare the readings. Keep total leakage and leakage to outdoors separate, and use the same test pressure, configuration and method for both records. Model a documented operating leakage flow and relevant air-to-surroundings temperature difference. The electric-input equivalent also requires explicit operating hours and a compatible effective COP. Do not enter CFM25 from a pressurized duct test as operating airflow.