We’re turning over most of this month’s editorial page to letters from readers. We always appreciate hearing from our audience, whether or not you agree with something we’ve written.
Input from readers is the best way to know if you like our content or if we missed the point in our recent coverage of an issue. Our letters this month touch on a potentially important regulatory change for flex duct possibly coming to California and other states, and the ongoing industry struggle to attract young workers.
If you have ideas for an article or just want to let us know how we’re doing, please email me at email@example.com.
Flex duct limit not supported
The Air Duct Council emphatically disagrees with the proposed arbitrary 5-foot length limit of flexible air ducts for residential applications in the next edition of the Uniform Mechanical Code (see “Being inflexible?” in this month’s issue). No technical justification has been provided to support this limitation and thus it is neither warranted nor justified.
All air ducts exhibit pressure loss due to friction regardless of the material the ducts are made from. Each duct type will exhibit different friction characteristics — some more, some less than others — that is unique to the duct type and material. The important aspect is to properly size all ducts to account for the pressure-drop characteristic associated with whatever type of duct material is being used. In addition, air ducts should be installed per applicable industry standards and per the manufacturer’s requirements, regardless of which duct type is used.
Due to the helical nature of the inner liner and the roughness factor of the materials used to manufacture flexible ducts, the pressure drop per foot is generally higher than that of the same diameter smooth galvanized pipe. When sizing ducts per the Air Conditioning Contractors of America’s Manual D, as required by the codes, the indicated diameter of a flexible duct run may well be larger than if sized using smooth galvanized duct. A properly sized duct system that uses flexible air duct will take the pressure drop characteristic and difference of the flexible duct material into account and thus the expected performance will be achieved.
Flexible air ducts have been installed throughout the country for more than 40 years without an arbitrary length limitation. The proposed code change to limit the length of flexible air ducts to 5 feet in residential applications, suggested for inclusion in the 2018 UMC, is not substantiated nor warranted.
John R. Falk, president
Air Duct Council
Article made good points
Regarding the article “Mutually attractive? Apprenticeships offer alternative career opportunities to millennials — if you can get them involved” (February 2017 Snips) by Audrey LaForest, I would like to get a copy to send to my state’s legislators in Maryland.
I said and wrote many of the same things in this article. In my education I had what most people do not have, a great father as a mentor, a great mother and good educators. I was educated in shop classes when they existed in junior high school. That was my only formal education in the arts of drawing for architecture and engineering, wood and metal shops where I learned the basics. Of course, my life experiences in this area provided additional training by ranch farming.
In a short five to 10 years later after taking those classes, our public school system eliminated shop classes and home economics classes. Today we see the results: a lack of qualified people to do the work in the trades with skills equal to or greater than a four-year degree.
Mike Rowe of “Dirty Jobs” fame said it clearly: Unless people get started early enough to develop a passion for skilled, hands-on work that uses high-IQ thinking, our service economy and population in general will suffer. It has and continues to this day.
H. Lance Bent, CEO
Melroy Plumbing & Heating Inc.