Say ‘No’ to IAPMO Duct Proposal, NAHB Says

Filed in Codes and Regulations, Design, Technology by on October 26, 2017 3 Comments

ductsThe International Association of Plumbing and Mechanical Officials (IAPMO) is preparing to vote on a change to the Uniform Mechanical Code (UMC) that would add at least $5,000 to the cost of a new home in California and the five other states that adopt it – and serve as the nose under the tent for other code-making bodies who may follow suit.

If approved by IAPMO’s standards council on Nov. 15, builders would be limited to using no more than five feet of flexible duct when installing HVAC systems in single-family, duplex, townhouse and multifamily residences.

IAPMO’s technical committee rejected this change by a two-thirds margin, but deep-pocketed proponents interested in expanding sheet metal jobs and selling more sheet metal ductwork voted against the technical committee at a recent IAPMO hearing.

Now, the issue will have to be resolved by IAPMO’s Standards Council, which will choose between defending the integrity of the IAPMO ANSI-accredited code development process or bowing to pressure from labor unions and manufacturers that benefit from forcing the use of metal ducts.

“No other model code or standard, including UL 181, NFPA 90A, the International Mechanical Code or the IRC limits the length of flexible ductwork,” said Jeffrey Shapiro, P.E., a consultant working to preserve their use.

“Likewise, the UMC has allowed the use of flexible ductwork in residential occupancies for decades without a length restriction. Nothing that’s been brought forward in this proposal warrants changing that now.”

The $5,000 in added costs estimate means that more than 700,000 additional California households would be priced out of a new home – exacerbating an already existing affordability crisis in the Golden State. And that estimate is conservative: Depending on the home’s plan, costs could be as high as $9,000 more per project, according to research from the California Building Industry Association.

“The technical committee gave a firm ‘no’ to this proposal in its meetings and in public comments. The standards council needs to reject the flexible duct restriction. Cost-effective construction must win out over special interests,” Shapiro said.

Comments on the proposal will be accepted until Oct. 31 and can be emailed to Gabriella Davis at IAPMO. For additional information, contact NAHB Senior Program ManAger for Energy Efficiency Don Surrena.

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Comments (3)

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  1. We say NO to this code change. We are a 55 year old HVAC company in Northern New Jersey which installs primarily new construction ducted HVAC systems. We have used flex ductwork in unconditioned spaces for years with no problems. When the energy codes changed we had to start sealing and insulating our sheet metal duct systems in basements. That code change forced us to start running insulated sheet metal trunk lines with flex duct for the branch lines because the labor required to install the sheet metal branch lines, seal and insulate the fittings was too cumbersome. It is also very difficult to find duct connection leaks when testing the final installed system. When properly installed flex duct is the perfect fit for a insulated and sealed duct system.

  2. Brian McDonald says:

    No real reason not to install insulated flexible ducts when properly installed.
    And isn’t that the real problem?
    Proper installation is the key to every aspect of construction.
    When manufacturer specs are followed things work as they should.

    The $5,000.00 additional cost sounds like it could be a per system cost.
    Two systems equals $10,000.00 additional cost, that’s a lot to force on someone.
    If they want to pay for the additional cost it’s their option; just like granite counter tops and stainless steel appliances.

    • You hit on a key factor, Brian. “Properly installed” is the root of most of the problems that have plagued the building industry for the past several decades. As a builder-turned-remodeler during the downturn, I can’t begin to count the number of “IM-properly installed” systems I’ve seen. From my Engineering days back in the ’70’s, there’s a couple of terms that come to mind – “Lamina Flow” and “Turbulent Flow”. Lamina flow requires smooth piping with as few turns as possible and is far less restrictive than the Turbulent Flow that occurs in the absence of smooth piping and presence of more bends. Most of the flex duct systems I’ve seen look like a gaggle of snakes having an orgy. The loss of flow efficiency in these systems has to be made up by bigger capacity – which pushes up the cost of the system. It’s definitely an area that could stand a lot of improvement. And like most things with the building code, rationality doesn’t seem to be a factor.

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