Should Duct Work Be Custom or PreFab?

[DavidNJ]

Of the installers I've talked to, two fabricate their own. The rest by sections and assemble. One of the installers who fabricates his own said a quick way to tell is the prefabricated sections are 5', the ones he makes are 8' because that is the sheet side. My guess is the prefab ones are made from rolls rather than sheets.

Which is better? After they are sealed is their a performance difference, the custom fabrication will have fewer joints? Which is more likely to be better quality? Which will be easier to maintain if there is a problem, the prefabricated sections presumably can be purchased from a variety of sources?

[ACFIXR]

Of the installers I've talked to, two fabricate their own. The rest by sections and assemble. One of the installers who fabricates his own said a quick way to tell is the prefabricated sections are 5', the ones he makes are 8' because that is the sheet side. My guess is the prefab ones are made from rolls rather than sheets.

Which is better? After they are sealed is their a performance difference, the custom fabrication will have fewer joints? Which is more likely to be better quality? Which will be easier to maintain if there is a problem, the prefabricated sections presumably can be purchased from a variety of sources?



The best duct that I have bought thru the years is the duct made by computerized plasma machines. the duct sections are made in 5' sections usually. This is also cheaper than custom made duct, quite a bit because it is so fast and efficient and the metal comes in huge rolls. The joints and gauge of metal separates the high quality to chincy. High quality duct is usually 24 or 26 gauge with pittsburg joints. I never use snap lock.

[Todd S 2]

Six to one, half a dozen the other. No differance on small residental jobs, normally.

[REP]

For 30 Plus years I have used premade duct with snap locks sized by me to be correct.
It dosen't matter how its made as long as Its metal.sized correctly and sealed.

[skippedover]

Manual 'D' sizing doesn't specify who makes the duct. It doesn't matter. What matters is that it is made from the proper materials for the job and is sealed and otherwise installed so as to have the lowest resistance to airflow and balanced air distribution. I doubt you can find a company anywhere that makes all thier own ducts. Somewhere they put in a short length of flex or other non-local product.

[DavidNJ]

Question: are special tools required for the Pittsburgh joint or snaplock? It looks like the Pittsburgh joint may require something.

http://hvac-talk.com/vbb/attachment.php?attachmentid=103622&stc=1&d=1277144993

Is some form of silicon sealant also used on the joints when they are assembled, or silicon sealant/adhesive? In engine building silicon sealant is de rigueur for water passages, exhaust manifolds, and intake manifolds, especially sealing to the lifter valley.

[ACFIXR]

Seal joint afterwards with DS321

Quick quiz;
what do the following have in common?
A. tools made in taiwan
B. cars made in russia
C. clothes made in mexico
D. furniture from ikea
E. snap lock duct

[jpb2]

I agree with sized and sealed propperly no dif. In my territory it's 50/50 factory trunk to shop made.

[t527ed]

For 30 Plus years I have used premade duct with snap locks sized by me to be correct.
It dosen't matter how its made as long as Its metal.sized correctly and sealed.


:ditto::ditto:

[energy star]

You can buy 8' or 10' duct from many supply houses. Just use mastic on all seams when duct is put together. The longer the duct the faster!!!!!

[tomjules]

For 30 Plus years I have used premade duct with snap locks sized by me to be correct.
It dosen't matter how its made as long as Its metal.sized correctly and sealed.


Most of the prefab duct sold in my area is 28ga. Couple that with the newer ECM motors that will try to deliver the full CFM amount, and you'll know soon if you're duct is undersized (Banging).

[jpb2]

Custom can be undersized as well. Bad install is bad however you slice it. There is a contractor here who makes "regular size " duct for almost all his installs. 24" sheet 28 ga. 14 3/4 x 8 8' long. It's custom though.

[mark beiser]

Question: are special tools required for the Pittsburgh joint or snaplock? It looks like the Pittsburgh joint may require something.

A hammer.

There are air and electric powered tools for making the job quick and easy.

[DavidNJ]

There are lots of different sealers. Is there any reason one is preferred over another?

Also, in most of the shots the sealer is applied to completed duct. Is there a reason it isn't placed in the snaplock or Pittsburgh joint groove prior to assembly?