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Message
Brand new AC and vents in living room are leaking badly
Posted on 6/6/26 at 9:31 pm
Posted on 6/6/26 at 9:31 pm
Installers came back and said everything is checking out and there is nothing to do. I am at a loss. It is brand new. The whole house cools except the living room - it stays several degrees warmer. It's not just when it's sunny and hot, even days like today in the 70s it cannot keep up. What is going on?!?!
7
Posted on 6/6/26 at 9:38 pm to rpg37
How are they leaking?
Posted on 6/6/26 at 9:39 pm to Trout Bandit
Extreme condensation on the vent itself.
And not only is the system brand new, the house was regutted. Eight month renovation. They did all the duct work and work themselves.
And not only is the system brand new, the house was regutted. Eight month renovation. They did all the duct work and work themselves.
This post was edited on 6/6/26 at 9:41 pm
Posted on 6/6/26 at 11:13 pm to rpg37
I upgraded one of our two units and ended up having to replace the ductwork with R8. Original R4 could not handle the additional runtime of the new, high efficiency unit. All of our vents were also sweating before changing the ductwork.
Posted on 6/6/26 at 11:17 pm to tg9r
quote:
I upgraded one of our two units and ended up having to replace the ductwork with R8. Original R4 could not handle the additional runtime of the new, high efficiency unit. All of our vents were also sweating before changing the ductwork.
How did y'all make this conclusion? I am frustrated for a brand new system and HVAC guys coming back once already they would not identify this, unless it's a down the road item.
Posted on 6/7/26 at 12:26 am to rpg37
I’ll have to defer to the experts on the board for this one. But I do have a couple of observations.
I see you are on the coast, so I know the air is humid as hell down there. For some reason or other, the humidity is too high inside of your house. You may simply need to add some weatherstripping. You may have duct leaks in your attic (which pulls unconditioned air into your house).
As a last resort, you could add a dehumidifier.
Your unit could be oversized, which causes short-cycling. This is not likely considering your other complaint about cooling.
I see you are on the coast, so I know the air is humid as hell down there. For some reason or other, the humidity is too high inside of your house. You may simply need to add some weatherstripping. You may have duct leaks in your attic (which pulls unconditioned air into your house).
As a last resort, you could add a dehumidifier.
Your unit could be oversized, which causes short-cycling. This is not likely considering your other complaint about cooling.
Posted on 6/7/26 at 1:10 am to rpg37
It would very well be “equipment” (refrigerant pressures, etc) is checking out to be normal, particularly if the house, other than the living room, is cooling down properly. As you describe it, sounds as though it is a duct related issue with the living room - size (diameter), sealing, a leak/tear/kink in that duct, damper(s) inside the living room duct(s) that control air flow are not fully open, …..so on.
Do you have an infrared temperature thermometer that you can measure the temperature of the air exiting the supply ducts in the living room, and compare it to the air temperature entering the return plenum? That is referred to as the temperature split - one usually looking for a split of 16-20 F depending on humidity in the house, time of day measured, etc. (Note: placing a thermometer inside the duct is more accurate but for a temperature split calculation an infrared thermometer measurement is OK ).
HVAC tech that came out to check the system should have measured temperatures and temperature splits at several supply duct locations in the house, plus the living room - did they? The temperature splits at vents with longest duct runs from the supply plenum will usually be lower than the shorter duct runs.
Do you have an infrared temperature thermometer that you can measure the temperature of the air exiting the supply ducts in the living room, and compare it to the air temperature entering the return plenum? That is referred to as the temperature split - one usually looking for a split of 16-20 F depending on humidity in the house, time of day measured, etc. (Note: placing a thermometer inside the duct is more accurate but for a temperature split calculation an infrared thermometer measurement is OK ).
HVAC tech that came out to check the system should have measured temperatures and temperature splits at several supply duct locations in the house, plus the living room - did they? The temperature splits at vents with longest duct runs from the supply plenum will usually be lower than the shorter duct runs.
This post was edited on 6/7/26 at 1:37 pm
Posted on 6/7/26 at 6:53 am to CrawDude
Find the coolest room in your place.
Close the damper in duct just a wee bit.
Open damper just a wee bit in warmest area.
OR have a return installed in warm room.
Close the damper in duct just a wee bit.
Open damper just a wee bit in warmest area.
OR have a return installed in warm room.
Posted on 6/7/26 at 7:00 am to Bayou
What is your run time looking like and what is the set humidity level on the unit? Our new system is variable speed and runs when the humidity level gets too high, but at a very lo speed. When first installed I had one duct sweating, but after a tweak of the humidity level, it went away.
quote:
have a return installed in warm room.
Posted on 6/7/26 at 7:47 am to rpg37
quote:
Installers came back and said everything is checking out and there is nothing to do.
Lies. They obviously don’t know what they are doing or looking at.
Posted on 6/7/26 at 12:41 pm to rpg37
Happened to us once and we thought the vents were leaking.
Turns out the roof was leaking and dripping on the duct work and running down to the vents.
Turns out the roof was leaking and dripping on the duct work and running down to the vents.
Posted on 6/7/26 at 4:33 pm to Spankum
quote:
I’ll have to defer to the experts on the board for this one. But I do have a couple of observations.
I see you are on the coast, so I know the air is humid as hell down there. For some reason or other, the humidity is too high inside of your house. You may simply need to add some weatherstripping. You may have duct leaks in your attic (which pulls unconditioned air into your house).
As a last resort, you could add a dehumidifier.
It is definitely sticky/muggy inside the house. We have had heavy rain the past couple weeks and it's been nasty outside. Not hot, but humid, thick air. It is an historical home and we have lots of doors, windows, etc. that have some seepage. We are doing a layer of insulation this week actually under the house which will seal off those small gaps in the joints of the original flooring.
I have been thinking of a dehumidifier, also...maybe not for the thought process you are bringing it up...why?
Posted on 6/7/26 at 5:54 pm to rpg37
Just got home and the home is holding 77 degrees and the vents leaking/condensating has now moved to two more vents in the foyer - including the vent closest to the AC unit itself.
Posted on 6/8/26 at 6:33 am to Spankum
quote:
Your unit could be oversized, which causes short-cycling
My money is on this and I almost let an HVAC guy talk me into this.
Then a more knowledgeable HVAC company taught me that oversizing a unit (while run time decreases) will present moisture issues as it cools the house quicker and doesn't have enough time to draw out the moisture.
OP, how far away from the return air is your living room?
Posted on 6/8/26 at 12:43 pm to rpg37
quote:
It is an historical home and we have lots of doors, windows, etc. that have some seepage. We are doing a layer of insulation this week actually under the house which will seal off those small gaps in the joints of the original flooring.
This is an important piece of information - historical home. You can have perfectly operating HVAC system and still be dealing with the issues you describing if the house is leaky as a sieve.
Have you had a blower door test performed that measures air filtration and identifies the leaky areas in the house in regards to outside air filtration? It’s not that expensive of a test all things considered (I had one done about 4 years ago at it was $350 then), and some utility companies will do it for free. Infrared cameras & smoke pens will be used to find significant areas of air infiltration in the house if the blower door test shows high levels of air leakage.
Also remember that basic insulation is a thermal barrier to heat and cold, not a vapor (moisture) barrier. Adding insulation though important is not the solution to a potentially leaky house. High air infiltration areas - doors, windows, air leaks from attic, air leaks from floor if the house is raised, etc need to be sealed.
If you have not heard of a blower door test here is video to get you started LINK. It’s required by code in many areas of the USA in new construction, or major renovation. Tons of articles and Y/T videos on the web. If you haven’t have this done, stop throwing $ on possible solutions until such time that you know what you are dealing with in regards to air infiltration in your historical home.
Posted on 6/8/26 at 12:50 pm to CrawDude
The house is elevated and we are having insulation done under the home this week. The jumper in the return in the living room came back good on tests. At the end of the day, he says the humidty in the house is high - and it is. We are going to re-evaluate after the insulation in the flooring is done. I also purchased a dehumidifier hoping the conjunction of both helps eliminate the issue.
Posted on 6/8/26 at 4:24 pm to TaderSalad
quote:
My money is on this and I almost let an HVAC guy talk me into this.
That's the one he had in his inventory.
Posted on 6/8/26 at 10:34 pm to rpg37
quote:
I have been thinking of a dehumidifier, also...maybe not for the thought process you are bringing it up...why?
Sorry…I should have checked back on this thread sooner. In my mind, there are only two reasons that there should be condensation on an A/C register. That would be:
1. The metal register is physically too cold.. this one can’t happen because of the way air conditioners work. They can’t produce air that is refrigerated temperature because it warms up as it passes through the ductwork.
2. The air surrounding the register is too humid. This is always the reason. It may be because of infiltration from the outside (which as I mentioned is caused by the house not being “tight” enough. In my case, I had a family member that was taking extremely long showers without using the vent fan in the bathroom.
While you are undertaking this, at Lowes or Home Depot you can get all kinds of weatherstripping. Don’t forget the little plates that cover electrical outlets, light fixtures,etc…those leak a lot of air.
ETA: I am curious…you say you are adding insulation to the crawl space….are you spraying foam or some other method?
This post was edited on 6/8/26 at 10:39 pm
Posted on 6/9/26 at 10:15 am to Spankum
quote:
ETA: I am curious…you say you are adding insulation to the crawl space….are you spraying foam or some other method?
Spraying an inch of foam under all the flooring.
We have weatherstripping but are looking to improve it some as well at doors. Windows are tough. Also, going to be looking at adding some shade.
Posted on 6/9/26 at 10:50 am to rpg37
The spray foam should help a lot with air infiltration from the floor.
Since you are fighting all of the same shite I did, you would do well to get yourself one of those pistol grip remote IR thermometers. They are only about $20 and you can do things like check temp of air coming out of your vents, search ductwork for leaks, and even check to see if they missed any spots on your spray insulating job.
As for the shade, I got a roll of shade screen from Lowes and replaced all of my window screen with shade screens. Just took a single afternoon to do all of my windows.
Since you are fighting all of the same shite I did, you would do well to get yourself one of those pistol grip remote IR thermometers. They are only about $20 and you can do things like check temp of air coming out of your vents, search ductwork for leaks, and even check to see if they missed any spots on your spray insulating job.
As for the shade, I got a roll of shade screen from Lowes and replaced all of my window screen with shade screens. Just took a single afternoon to do all of my windows.
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