Duct Leakage Testing

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Duct Leakage Testing


  • Need for duct leakage testing
  • Duct leakage testing standards and regulations
  • Performing duct leakage testing

Why Test Ducts for Leakage?

Conserve energy
  • 10-30°/o of heated/cooled air lost through ductwork
  • Leaky supply ducts don’t delivery air where needed
  • Leaky return ducts add load
Indoor Air Quality

Leaky returns can pull in air from uncontrolled spaces,causing

  • Humidity problems
  • Contaminants

IAQ, Comfort, Energy issues caused by leakage from HVAC System

System Leakage = Duct Leakage + Equipment Leakage + Accessory Leakage

Scope of presentation = Duct leakage



  • SMACNA HVAC Air Duct Leakage Test manual, First edition, 1985
  • ASHRAE 90.1 (Proposed)
  • Project specifications
  • California Title 24 -7 residential testing required if ahu/furnace in garage or ducts in non-conditioned space (attic)


  • BS EN 12237:2003 – Circular Ductwork
  • BS EN 1507:2006 – Rectangular Ductwork
  • DW/143 (HVAC-A practical guide to Ductwork leakage testing)
  • Eurovent 2/2 (Air leakage rate in sheet metal air distribution systems)

Transverse Joint

  • Duct-to-duct, -branch,-tap, etc.

Longitudinal Seam

  • Joining of 2 edges in direction of airflow


  • Rod, wire, tubing, etc.

Sealing not required

  • Spiral seams
  • Screws & fasteners
  • Damper rods

How to Test Duct Leakage (Basic)

  • Identify ductwork section to be tested – Calculated surface area
  • Seal ductwork
  • Pressurize ductwork to specified level
  • Measure flow required to maintain duct pressure
  • Compare to standards

Duct Leakage Measurements

0/o of Flow requirements
  • Problem: Disregards size of ductwork & static pressure
  • i.e. 1°/o of flow on 3900 cfm system = 39 cfm. If 1300 ft2 duct area = 3 cfm leakage I 100 ft2 300 ft2 duct area = 13 cfm leakage I 100 ft2
Test pressure requirements
  • Problem: Test pressure higher than duct design
  • i.e. testing system designed for 2 in H20 operation at 10 in H20
Need to consider
  • Surface area of ductwork
Type of ductwork (round, rectangular)
  • Static pressure