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Duct Gauge, Locking Caps, Flex Duct, And Mechanical Ventilation

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As we’ve learned previously, the development of the national model codes, and the various state building codes, is a long process that is designed to include input from affected parties in order to ensure that our buildings provide a safe environment in which we can live and work.

The volunteer members of the ACCA Codes Committee assist the association in beneficially representing the HVACR contracting community in the code development and administration processes that affect our industry. This includes identification of code sections that require modification, development of code change proposals, providing testimony at public hearings, and serving on various technical committees and task groups within the International Association of Plumbing and Mechanical Officials (IAPMO), the International Code Council (ICC), and the National Fire Protection Association (NFPA).

Going forward, the ACCA Codes Committee seeks to take on a more proactive approach to our advocacy activities, eventually becoming a clearinghouse for national and state code development information. This was spurred by four issues that have come about in the past few years.

Duct Gauge
The 2009 International Mechanical Code (IMC) and International Residential Code (IRC) changed the sheet metal thickness requirement for 14” residential ducts from 30 gauge to 28 gauge, an increase in thickness from 0.013 in to 0.016 in. The change had no technical merit and actually made no sense for where it was implemented, but it passed the committee and public hearing votes and became a part of the model codes regardless. It wasn’t until the 2009 codes started being enforced that the industry noted the unnecessary increase in duct gauge. A coalition of industry groups moved quickly to correct this oversight. For more details, check out the article, “A Case of Commercial Requirements Being Applied In Residential Applications.”

Locking Caps
The 2009 IMC & IRC also saw a new requirement for outdoor refrigerant lines: all access ports must be fitted with locking-type tamper-resistant caps. This change was introduced in order to counter a growing trend of teens who huff R-22. Never mind that the statistics used for substantiation were misleading at best, or that the change has huge aggregate financial repercussions, the proposal passed. The jury is still out about the effectiveness of this solution.

Flex Duct
The 2015 IAPMO Uniform Mechanical Code (UMC) now has a provision which limits the use of flex duct in commercial applications to no more than five feet in length. The original proposal, submitted and championed by a sheet metal workers union, was disapproved by the technical committee. It was clearly biased, poorly reasoned, and unnecessarily restricted a designer’s options because of the possibility of improper installation of flex duct. However, a public comment to the committee’s rejection was (narrowly) approved, and only by excepting residential applications from the five foot requirement.

Mechanical Ventilation
Section 401.2 of the 2012 IMC requires ventilation for all occupied spaces, and allows the designer to choose between natural and mechanical, depending on the building’s need. Unlike the 2009 edition of the code, the 2012 (and now 2015) code also has an air infiltration requirement in the same section, which points to a testing procedure in the International Energy Conservation Code (IECC). This new requirement creates a Catch-22: the mechanical contractor may choose natural ventilation, but get failed by the inspector at the end because of a test-out requirement for the entire home. It is effectively a convoluted requirement for mechanical ventilation. ACCA is currently working to get this section reverted to the 2009 version, which simply allowed either natural or mechanical ventilation.

Your Participation Is Essential
The issues above got to that point because the HVACR contracting community has largely been absent in the code development process. Though staff and the committee have monitored the process for years, there hasn’t been enough manpower to make the impact our industry deserves. This is most true when it comes to the public hearings. As on-the-ground practitioners, your testimony in favor of, or in opposition to specific code change proposals carries a lot of weight. After all, you are the ones ultimately charged with complying with the code requirements. Having contractors speak out about the feasibility, practicality, and substantiation for provisions in the code can make the difference between having code provisions that make sense, or codes that don’t.

This year’s code cycle ends in October at the ICC Public Comment Hearings in Long Beach, CA, during which we’ll be finalizing the 2018 IMC, IFGC, and IRC (mechanical provisions). Keep a lookout in the ACCA Insider for a summary of the proposed changes to be discussed, as well as other ACCA codes activity information. Anyone interested in becoming more involved in the code development process is encouraged to contact Luis Escobar, ACCA Manager of Codes & Standards, at in order to find the best way for you to serve.

Luis Escobar

Posted In: ACCA Now, Technical Tips

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