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  1. #1
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    Aug 2011
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    Ductwork; 26 versus 30 gauge

    Im looking at two competing bids for a complete HVAC upgrade. One contractor is bidding 30 gauge ductwork and the second 26 gauge. Ive read that 30 gauge is too thin to be used in residential ductwork. Whats the opinion of the professionals?

    Just to be clear, there are other differences in these proposals to be evaluated and ductwork gauge is just one item. Im just trying to rank the severity of this difference.

  2. #2
    Join Date
    Aug 2011
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    568

    Hmm

    Quote Originally Posted by Dale_R View Post
    Im looking at two competing bids for a complete HVAC upgrade. One contractor is bidding 30 gauge ductwork and the second 26 gauge. Ive read that 30 gauge is too thin to be used in residential ductwork. Whats the opinion of the professionals?

    Just to be clear, there are other differences in these proposals to be evaluated and ductwork gauge is just one item. Im just trying to rank the severity of this difference.
    26 gauge is a lttle more expensive and heavier duty! i.e. it has more metal in it! if you like the guy with the 30 gauge metal, you can always ask him how much extra is the 26 gauge up grade. good luck!

  3. #3
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    Jun 2011
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    Pa.
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    Sounds to me that the guy with the 30 gauge may be buying it from a supply house who sells it pre made.I dont know to many sheet metal shops who make duct work in 30.I prefer 26 myself and think a sheet metal shop that makes it in house is much better than the pre made.

  4. #4
    Join Date
    Feb 2009
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    Portland OR
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    30 gauge is also known as WA or Warm Air ductwork in my next of the woods. But if we are doing square duct or anything over 12" round we do 24 to 26 gauge.

  5. #5
    Join Date
    Nov 2006
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    SC
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    30 gage is typically prefab and 24/26 is typically shop made for your specific job. I definitely prefer the heavier metal for its durability and rigidity. However, it is entirely possible to design a properly functioning system using 30 gage metal.
    I don't know who you are getting bids from, but a guy who makes his own ductwork has been in business for a while and is more likely to know what he's doing.
    While prefab duct can and is used for quality installs, any joe blow can purchase it, so there are many, many more hack jobs out there using 30 gage.
    BTW, I sometimes use prefab 30 gage myself.

  6. #6
    Join Date
    Aug 2011
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    568
    as far as using fab duct from supply houses, it's the only way to go. it's not cost effective to make standard size duct work. with all the available fittings and reducing products i really don't see the benefit of making basic sized trunk lines, now as far as plenums and such, having a small shear/pittsburgh machine,4 ft. break is the way to go, or a really large shop, that has a lot of installs, maybe a plazma cutter/8 ft. break/and other accesaries!

  7. #7
    Join Date
    Dec 2010
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    The Quad-Cities area (midwest).
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    We fabricate our duct and sometimes 30 ga. on small fittings works. We use 26ga. mostly but sometimes, when the ductwork (size) requires it, we will use 24 or even 22ga.

  8. #8
    Join Date
    Jun 2005
    Location
    Winston-Salem NC
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    If I use square duct, it is 26ga in residential non-exposed settings and 24ga if it is exposed, and I use 24ga if it is a commercial setting.

    My favorite ex-employer is my supplier from his sheet metal shop and I take a hit on my profit margin because I buy the good stuff, but it makes me happy to do it right.

  9. #9
    Join Date
    Jun 2010
    Location
    Philadelphia PA
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    2,190
    New IRC eliminates 30 ga. The real problem was the "Economy" grade duct was sub 30 ga they used 0.011 vs 0.013 ( the min for 30 the other problem is the galvinize coating has now gone below G60 so the material is not only too light but also will likely rust a lot sooner

    Go with the guy with 26ga quote, he is doing it right
    You have got to learn from other people's mistakes! Because God knows you don't live long enough to make them all yourself !!!!!!!!

  10. #10

    Good question!

    This is the Ask Our Pro's forum. In order to post a response here, you must have verified qualifications and have been approved by the AOP Committee. You may ask a question by starting a new thread.

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    Last edited by jpsmith1cm; 11-28-2012 at 06:24 AM. Reason: non AOP member

  11. #11
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    Oct 2010
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    Anderson, South Carolina, United States
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    Any plenums/square duct over 12x12x12 should be a heavier gauge than 30, even when cross broken they tend to have duct banging issues because the metal isn't rigid enough IMO. All our fabricated duct is 24/26 gauge. We buy pre fan for round duct and most supply houses don't carry anything but small diameter round in 26 gauge (single wall vent pipe 4-6) so we use the 30 for trunk lines. It's more cost effective as well.

  12. #12
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    Aug 2011
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    Northeast and Southwest
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    Thanks to everyone for contributing their expertise!

    I appreciate all of the above inputs. I'm impressed with the variety of the responses; some saying 30 ga. is OK while others saying to only use 26 ga. In all cases, the contributors indicate that they can deliver a quality product using either sheetmetal ga.

    In the end, I decided to use the company that uses 26 ga. but there were many other factors that came into play that made a difference. The system was for my daughters house in Massachusetts and is a hydro-air system with a gas fueled Viessmann boiler, two separate heating/cooling zones, and an indirect fired water heater. It's a beautiful system that works very well (maybe because I ran my own Manual J and did my own equipment sizing calculations to compare against the contractor's sizing).

    Turns out that the installer subs out his ductwork fab where he can get 24 hour turnaround. They used to fab sheetmetal but gave it up several years ago.

    Thanks guys!

  13. #13
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    Western PA
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    Tinman1120This is the Ask Our Pro's forum. In order to post a response here, you must have verified qualifications and have been approved by the AOP Committee. You may ask a question by starting a new thread.

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