Ductwork is one of those things that doesn’t get much attention as long as it works and doesn’t leak too much.
That is, until something is suggested by a standards-writing organization that the HVAC construction industry doesn’t uniformly agree with.
And that’s what has happened since International Association of Plumbing and Mechanical Officials proposed limiting the use of flexible duct to runs of 5 feet or less. They note that flex duct loses energy through friction, and limiting its use and length would minimize such loses, I presume.
In many parts of the country, such as the Midwest, the use of flex duct is pretty rare. But in others, such as the Southwest, it’s a very popular alternative to traditional ductwork fabrication.
You might have seen the letter to the editor in December’s SNIPS from Chris Van Rite of M&M Manufacturing. As a manufacturer of sheet metal duct components, Rite and M&M support the proposal.
But those who make flex duct products, such as Hart & Cooley Inc., along with several industry associations, are strongly against it. They note that all ducts, regardless whether they’re made of metal or other materials, have friction-related pressure losses. The key to saving energy, they say, is proper installation and sizing.
The IAPMO is taking comments until Jan. 3, 2017. A final decision could come early in the spring. What do you think about it?
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