HVAC Duct Trunk Leaks

Reply

  #1  
Old 01-26-21, 08:55 PM
S
Member
Thread Starter
Join Date: Jan 2013
Location: USA
Posts: 432
Received 0 Votes on 0 Posts
HVAC Duct Trunk Leaks

The attic HVAC duct trunk has a hole in one of the seams approx. 1" wide. I can also feel air leaking from other seams in the trunk. Is this normal acceptable loss? Should I just use foam sealant or is there better methods to close off the leaks? Also, there are few dents in the trunk. I doubt it's worth replacing/fixing but didn't know if this would impact air flow..

The bedroom that's at the end of the trunk is freezing so I used the dampers to close off other rooms to redirect flow. The damper is really tight and doesn't seem to want to move more than a few inches in each direction. Also, some of them are covered in tape that need to be ripped to get access. I don't feel a leak but it is odd to me that they are not exposed.





 
  #2  
Old 01-27-21, 12:54 AM
Marq1's Avatar
Member
Join Date: Sep 2016
Location: USA MI
Posts: 7,095
Received 460 Votes on 429 Posts
Its acceptable only if your good loosing all the conditioned air to the attic.

All those joints need to be tightly an neatly sealed.

And how much energy do you think is being lost from an uninsulated main duct not to mention an attic that could use a lot more insulation?
 
  #3  
Old 01-27-21, 05:50 AM
J
Member
Join Date: Jan 2021
Location: United States
Posts: 39
Received 4 Votes on 4 Posts
I recommend you seal all of the leaks and insulate the main trunk.
Butyl foil HVAC tape is good for sealing that hole. I suspect that fabrication work has a lot of leaks, and butyl tape will be good for most of them.
You can use duct sealant for seams.
The main trunk needs foil faced fiberglass duct insulation. Closing leaks and insulating that trunk will make a noticeable difference.
For the leaks at the flexible duct connections, you could first try using cable ties and tighten with a cable tie gun. If that doesn't stop the leak then pull off the flexible ducts and use mastic and cable ties for a good seal.
Also recommend check the area for mold, particularly above and below the uninsulated trunk.
 
  #4  
Old 01-27-21, 06:06 AM
P
Group Moderator
Join Date: Mar 2003
Location: NC, USA
Posts: 24,689
Received 783 Votes on 720 Posts
You need to seal the holes. Clean the area so things can stick. I like quality aluminum foil tape for bigger holes. Then for seams I use duct putty which you paint or trowel on and it hardens sealing the holes. Then I would insulate your duct since it's running through a hot/cold attic.
 
  #5  
Old 01-27-21, 07:33 AM
D
Member
Join Date: Mar 2019
Location: USA
Posts: 110
Received 19 Votes on 18 Posts
I can vouch for the savings coming your way if you follow the advice given. Be sealing all the plenum leaks and replacing the plenum insulation from R6 to R8, my AC bill was but by 1/3. Your savings might be even better since your plenum is currently uninsulated and yours is used for both heat and A/C.

Your attic looks a lot like mine. The job sucks, but the payoff is worth it. I did it last spring when things warmed up enough to not require heat, but before it was hot enough to require A/C.
 
jrsick voted this post useful.
  #6  
Old 01-28-21, 08:37 PM
S
Member
Thread Starter
Join Date: Jan 2013
Location: USA
Posts: 432
Received 0 Votes on 0 Posts
Local HVAC guy came over. He said the trunk isn't wrapped because it has insulation on the inside? He noted that there was no moisture on the trunk. I can't see inside but a quick google shows that it's possible? Anyhow, he mentioned I could upgrade from R6 to R8 for the duck piping to the registers but he didn't think it would make a huge difference. He said every seam should have been sealed with HVAC tape including the many small holes (like why? how?). We also didn't notice any major leaks where the piping connects to the trunk.

Fixing the various leaks at the seams should be something I can tackle. For the seams, should I use tape or putty? The HVAC d00d said tape but putty was mentioned here. Tape would be easier.
 
  #7  
Old 01-28-21, 08:57 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 61,382
Received 1,399 Votes on 1,296 Posts
Foil tape is easy to use and does an excellent job of sealing.
The duct only needs to be reasonably clean as the tape has excellent glue on it.
If you have a sharp edge..... double the tape over it.
 
  #8  
Old 01-28-21, 09:51 PM
S
Member
Thread Starter
Join Date: Jan 2013
Location: USA
Posts: 432
Received 0 Votes on 0 Posts
Would a spray bottle with soapy water be enough to identify the leaks?
 
  #9  
Old 01-28-21, 10:23 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 61,382
Received 1,399 Votes on 1,296 Posts
The only problem with that idea is the tape won't stick to the wet soapy surface.
Usually all seams are done..... whether or not they're leaking.
 
  #10  
Old 01-29-21, 05:16 AM
J
Member
Join Date: Jan 2021
Location: United States
Posts: 39
Received 4 Votes on 4 Posts
You can use mastic foil backed tape for everything. Apply the tape at room temp if you can. Use a knife, vice scissors, to cut it and apply it to the surface with pressure.
Your soapy water plan will work, but I would recommend taping over any area that you are concerned about.
The mastic has strong grip and will last many years.
I mentioned duct sealant earlier, but the tape works well also. I like the liquid sealant to seal round duct seams, but you can do same with the tape.
 
  #11  
Old 01-29-21, 06:24 PM
S
Member
Thread Starter
Join Date: Jan 2013
Location: USA
Posts: 432
Received 0 Votes on 0 Posts
Thanks for the help. For the small holes, wouldnít a duck sealant be easier than to constantly cut small pieces of tape? Ton of small screw holes that I could patch up
 
  #12  
Old 01-29-21, 06:40 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 61,382
Received 1,399 Votes on 1,296 Posts
Why tons of small holes ? What have you got.... a ductpecker up there.
The choice is yours. Either method is effective.
 
  #13  
Old 01-29-21, 06:46 PM
S
Member
Thread Starter
Join Date: Jan 2013
Location: USA
Posts: 432
Received 0 Votes on 0 Posts
I canít blame the kids or the puppy for this.

Small Holes can be filled with putty and seams and big holes can be fixed with tape. Itís odd but just a ton of small holes and gaps here and there. Sloppy.
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: