City of Thornton Amendment to 2015 IECC Code Adoption

City of Thornton 2015 IECC Code Amendment

Duct Leakage Testing Requirements

The City of Thornton has amended the 2015 IECC Code to ensure compliance for residential duct leakage testing.

City of Thornton Amendment to 2015 IECC Code

Key Amendment Details

The City of Thornton has amended the 2015 IECC to require all duct systems to be tested and meet a maximum leakage amount on all new residential construction. This requirement applies regardless of the location of the duct system.

Ducted HVAC Systems - Location is No Longer a Factor

The City of Thornton has amended the 2015 IECC to require all duct systems to be tested and meet a maximum leakage amount on all new residential construction. This requirement applies regardless of the location of the duct system.

This amendment requires the duct leakage test to be passed as part of the rough mechanical inspection. Therefore, the test needs to be performed prior to the installation of insulation. For many of EnergyLogic's performance path clients, this will require an additional site visit. Please contact us to discuss how this change will affect our scope of work.

Adopted Amendments

  • Subsections N1103.3.3(R403.3.3) and N1103.3.4(R403.3.4) are hereby repealed in their entirety and replaced with the following: N1103.3.3 (R403.3.3) Duct testing (Mandatory). 66
  • Ducts shall be pressure tested to determine air leakage by a rough-in test. The total leakage shall be measured with a pressure differential of 0.1 inch w.g.(25 Pa) across the system, including the manufacturer’s air handler enclosure if installed at the time of the test. All registers shall be taped or otherwise sealed during the test.

  • The total leakage shall be less than or equal to 4 cubic feet per minute (113.3 L/min) per 100 square feet (9.29 m2) of conditioned floor area where the air handler is installed at the time of the test. Where the air handler is not installed at the time of the test, the total leakage shall be less than or equal to 3 cubic feet per minute (85 L/min) per 100 square feet (9.29 m2) of conditioned floor area.

Supporting Documentation

You can find the amendment document listed on The City of Thornton's website.

  • Navigate to the menu column on the right side of the page and find the Building News & Key Links section.
  • Click on the "Amendments to 2015 Codes" link to access the full PDF document. The 2015 IECC code option language specific to mandatory duct testing can be found on page 65 of the document.

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About the Author
Robby Schwarz

Robby Schwarz

Robby co-founded EnergyLogic with Steve Byers & Wynne Maggi in 2006. As Director of Builder Relations, Robby works closely with builders to achieve their efficiency goals, while keeping an eye on cost and cycle time. Learn more about Robby here.

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