HVAC duct air leaks?

I called out a possible air leak in the ceiling of a new construction home. However, I heard from my client that the builder cut out this area and claimed there was no leaking. They said that it was because it was a junction where three ducts were coming together, giving off a high heat signature. That just doesn’t sound kosher to me, and your input would be appreciated. Thanks.

HVAC duct air leak in ceiling combo_Fort Drive.jpg

Was this a 2 story with the duct between the floors or was there a attic above this area. Very possible to be just a signature if the duct was close to the dry wall does not have to be a air loss to transmit temps that is why I further investigate before I make a call

That’s a pretty significant heat variance for thermal transfer through both the duct and ceiling insulation.

I would describe it as a thermal anomaly, possibly an air leak in the ductwork. Then say it should be investigated and repaired as appropriate. If it’s possible to get up there, I would go check it myself.

If you get the chance, I would go back and look to see if they actually cut it out, then shoot it again to see if its still there. It wouldn’t be the first time that a builder claimed to have opened and determined there was no issue without actually doing so. Nor would it be the first time that a contractor fixed the problem you reported then told the builder/buyer the problem never existed.

This was between the 1st and second floor so was inaccessible. I don’t think there was any insulation either. Have you guys seen this before? Sounds like one of you thinks this heat transfer can happen even if there are no leaks. Any others? Thanks.

Scott one could almost make book that there is no insulation between the floors and no way to actually determine 100% without destructive observation but I have observed this when the duct is lying against the drywall especially if the contractor did not insulate the duct properly or no insulation do you know if flex duct or rigid was used between the floors most of the time flex duct insulation will not be as thick as insulation on rigid and will transmit temps quicker

Yep, was flex duct. So Charley, how would you have handled this? Do you think you would have called it out as something that needed further evaluation? Or just a thermal anomaly? I’m new to the IR field and trying to get a hang of how best to call things out. I did position this to my client as a “possible” leak in the HVAC ducts that needed further evaluation by an HVAC professional. Thanks.

First of all, leakage between floors, what is the worst that will happen?


It must be a T. This unlikely good duct design (?). It weighs more and is likely sitting on the ceiling.

My concern is that you called this out. The contractor cut it out to look at it ( I wish I could get them to do that even when I “know” there is a real problem)! Nothing found! What is the adverse condition? Condensation in the cooling mode maybe. But not identified today.

Leakage between floors gets real big with time. Can lights will heat up the entire joist bay across the uninsulated ceiling.

Below is leakage (between floors) from yesterdays insp that is likely leaking between the boot and the register grill. Told the client not to get excited, but may want to take it apart and caulk the fitting.

I recommend caution with limited access issues like this. I would just identify the location for the client. If it molds, they can cut it out, fix the duct leak and refinish the ceiling (in this case, it was done without cause). I don’t think anyone will like this call after nothing was found!

Your camera can find some very minor issues that look HUGE! I have an electric heater running in my office and I can see the wiring in the wall and ceiling, all the way to the sub-panel! I smelled something burning, which turned out to be my wood stove. As I was downloading scans, I took a look around and saw it…

Just be careful with what you call.
Just because you can see it, does not mean it’s a problem.

Try posting scans here before you report. That was the intention of this section from the beginning, but few use it.

Scott that was the reason that I asked you if it was a two story. I would have been very cautious about making a call on that due to in being between conditioned areas. I would have gone to the upper level floor above this if possible and scanned the floor above it. If if was significant air loss the floor above should have shown a thermal pattern between the joist. If it was just conduction between the duct and the ceiling of the first floor I would not have had a big concern based on the fact in the cooling mode the possibility of condensation on the first floor ceiling probably would never happened. I would have put in my report the slight possibility of condensation on the ceiling and ask the installing contractor to put in writing how the duct was installed and how the duct was insulated at the TEE if any. I would have placed the burden of proof on the contractor.

BTW I just recently placed the burden of proof on a contractor for a never lived in home concerning a plumbing drainage situation that was not visible during the inspection and the contractor on their letter head did provide the information needed to my client. A little communication between all parties goes along way as long as no one gets belligerent thinking they know everything.

Thanks Charley. I’m trying to figure out how anyone could tell the difference between an air leak or not in this situation without “further evaluation.” Do you think calling it out for further evaluation was appropriate in this case? Or just telling my client there “may be” some air leaking, but it does not appear to be affecting the airflow noticeably (i.e., putting it in perspective).

Scott from your pic it appears the area effected is near the middle of the room between the floor joist there should have been a thermal pattern on the ceiling and the the floor above if it was a air leak, heat rises. If the builder did in fact open the ceiling as you stated I would recommend returning and re scanning both the ceiling and the floor upstairs that should remove the guess work. No one without a thermal camera can further evaluate without destruction. Personally I would want more images before I told someone to tear out the drywall. I am not a fan of the word may.

OK, I really appreciate it. And last question please. If it in fact was an air leak, do you think it would show through carpet above the suspect location? I did not check the surface above (good suggestion), but am curious if you think it would show through carpet, or even hard wood. Again, rookie IR guy here. Thanks.

Yes it should show a pattern upstairs even with carpet if in fact it is a air leak just allow the furnace to operate for a extended period of time.

Sometimes owners want to be expert. That is the worst part in work. Experts mean experts. There is no alternative.
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Patrick how thoughtful of you to dredge up an ancient thread so that you can SPAM it with your very first non-member post.

Would it be accurate to say that VENT CAP SYSTEMS IS A SERIAL SPAMMER ?

Between floors duct leakage isn’t really an issue unless it’s large enough to prevent the conditioned air from going to it’s intended place. Duct between floors in conditioned space are not required to be insulated. The builder used flex duct cause it was easy and what they had and it was insulated but the junction was more than likely not. Heat moves to cold, hot air rises. What your seeing was probably the radiant heat coming off the metal and hitting the drywall. If there was a large amount of leakage suspected the builder should have ordered a duct test. If they were doing the 2009 IECC testing like here the builder would already have the numbers. If they were high they could have smoked the ducts to help find the leakage