What do you see wrong with this duct install???

Duct vapour barrier not sealed. Can lead to condensation in insulation when A/C is running…especially in very warm/hot humid weather.


Specifically speaking, what is you are looking at in the pictures that leads you to say that? Is it the white insulation visible on the large duct by hanger? Or are you looking at something else?

Outstide of an odd installation technique, I dont see anything wrong.

  • I take it you have never professionally installed duct:p :slight_smile: *

Plenty of overlap at the seams no condensation going on here.

Not properly supported and the duct laying against the insulation is not straight enough.

partially supported by a 2X4

Improper duct support. Metal (plumbers tape)

From the IMC:
603.10 Supports. Ducts shall be supported with approved
hangers at intervals not exceeding 10 feet (3048 mm) or by
other approved duct support systems designed in accordance
with the International Building Code. Flexible and other fac -
tory-made ducts shall be supported in accordance with the
manufacturer’s installation instructions.

Is the large trunk line metal snap lock wrapped in insulation? First thing I noticed is; why the hell did they put it so high up into the attic into the hotter area of attic? Next thing I see is it doesn’t look like professionally constructed connections where the flex joins the collars; no zip ties, hard cast or for that matter even duct (code) tape. Some of the flex connections are too close together (cause a drop in pressure along the trunk). just to name a few things.

The main trunk line was metal and plumbers strapping is the excepted method for metal duct, for flex duct its not allowed.

I did not have a problem with any of the supports and as for the small turn in the return air duct lying down on the attic insulation not a problem with me.

Master Chief now we are getting some where Thank you.

The trunk line is snap lock and yes they did not use wye connections on the two bottom connections and the two bottom connections should come off of the side not the bottom.

The ducts were installed in the hottest part of the attic because a upflow was installed in the up right position with the supply plenum on the top. should have used a horizontal or a downflow so the duct could be installed at a lower level.
They did use zip ties they were under the insulation as they should be. I did not have a a problem with the spacing of the drops.

I did not write up any corrective action on this just very poor craftmanship

For those of us who are not HVAC gurus, what is the functional problem with this installation?

When you just tap into a trunk line without a wye fitting you have to depend on static pressure on the trunk to get air flow to the register. Those two drops in the pic have less air flow than the ones with wyes.

I was taught to never install a drop on the bottom as it would be the first place any condensate in the line would exit the system. I like my ducts basically water tight.
I was taught by old men that had never looked at a code a book and basically I did not either and now I am old:)

The basic that I was taught when running duct (metal) was to alway start at the plenum with the trunk line. The seam in the snap lock duct is alway turned to the top of the run with the crimp end of the pipe pointing toward the register end of the run.

I always pre-insulated my duct before I screwed the joints together. A roll of insulation is 4 feet wide. A joint of pipe is 5 feet long so when you pre-insulate it leaves 1 foot of bare metal. You just simply pull the insulation down the duct to where you get to the first wye, makes a neat install. I also pre-insulated my wye’s which no one takes the time to do now days looks like slop. All of the seams in the insulation should be turned to the top of the duct and in line with the next section. I always tucked my seams and stapled every seam to where there was no pink showing. My nick name was NO PINK but when I finished it looked professional as if someone cared about their work even though not many people ever saw the work. Back in those days we did not have dumb HI’s that wanted to crawl under homes for money:roll:


I’ve got to have a picture of the upright in the attic (for my web site).

Do you have it?

Any condensation would go straight down those bottom duct’s, and although I like the way the trunk line is up high,(easy to get around) they could have saved 50% of the materials, if it was installed at the bottom. But you’re right, it sure is pretty.

I have one David but not a good quality Pic the platform was not very big and I was trying not to stick my feet through the ceiling. Sorry

Thanks for educating this ol’ HI:cool: I think I’ve got it, but I’m still a bit confused:shock:

So, lets say that main line was down resting on the insulation, and there is a duct directly under it (typical of many homes built in the 70s around here). Are you saying that the duct directly under the main line will have condensation issues?

What about the duct that has a proper wye to say a bedroom duct via flex line, but that flex line then turns down to the duct? Is that not a problem because it’s at the end of a line, not directly under the main line?

Oh, and how do you write up this kind of issue?