# Condensation from Ceiling AC Vent



## meth (Apr 22, 2008)

Hope you guys can help. I have condensation dripping from one of my AC vents in my bedroom. It only happens on real cold weather days, the vent is in the ceiling approximately 2 feet from an exterior wall that has a sliding glass door. My assumption is that the interior warm air from the room is meeting the cold air from the attic causing the condensation - thus dripping from the vent to the floor. If I close the vent, it becomes worse, if I leave it open it lessens a bit. This is the only vent it is occuring from and I have verified that there is no water source nearby. Could this be an issue that there is not enough insulation in the attic? What are your suggestions for correcting?


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## kennzz05 (Nov 11, 2008)

love your screenname go in the attic and im sure youll find the insulation has been moved away from that register it needas to be insulated around it


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## meth (Apr 22, 2008)

Thanks! I assumed that is the issue, however getting to that portion of the attic requires me to be a catortionist and slide in about 25ft on my stomach over the rafters. I plan on opening the side of the house in the spring and spraying some cellulose in over the existing insulation.


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## Marvin Gardens (Sep 30, 2008)

Just putting in more insulation will not stop the condensation. It will just make your insulation wet.

I suggest that you insulate the pipe also which will reduce the warm air coming in contact with the cold pipe.


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## meth (Apr 22, 2008)

Are you suggesting that I wrap the duct pipe in insulation?


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## Marvin Gardens (Sep 30, 2008)

meth said:


> Are you suggesting that I wrap the duct pipe in insulation?


Yes. Any time there is cold moist air meeting warm there will be condensation. Insulating it will reduce or eliminate the warm/cool surface.

What is happening is that you are getting some heated air going into the vent by convection and it warms the pipe. Then the cold moist air comes in contact with it and causes the moisture in the cold air to condense out and it forms dew on the pipe. Then gravity causes the droplets to run down the pipe and drip into your insulation.

This is why you need to insulate all duct work outside any conditioned space.


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## meth (Apr 22, 2008)

Sounds like an easy fix - Thanks!


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## Marvin Gardens (Sep 30, 2008)

meth said:


> Sounds like an easy fix - Thanks!


Except for the crawling on your belly to get to the pipe...:yes:


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## kennzz05 (Nov 11, 2008)

my bad i just assumed the pipe would have been insulated already only makes sense


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## meth (Apr 22, 2008)

Got up there and poked around a bit. It doesn't appear any of the insulation hs been disturbed. The pipe is an insulated flex pipe. I will need to address the insulation issue at a later date, however as a short term fix - what do you guys think about this - If i take the vent cover off from the inside room - stuff some insulation inside and close it back up? That should insulate the warm air from the inside penetrating the attic colder air? I know this is only a short term fix until I can crawl in and insulate the area, as well as hire someone to come in and blow in some insulation to the entire area.


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## Marvin Gardens (Sep 30, 2008)

meth said:


> Got up there and poked around a bit. It doesn't appear any of the insulation hs been disturbed. The pipe is an insulated flex pipe. I will need to address the insulation issue at a later date, however as a short term fix - what do you guys think about this - If i take the vent cover off from the inside room - stuff some insulation inside and close it back up? That should insulate the warm air from the inside penetrating the attic colder air? I know this is only a short term fix until I can crawl in and insulate the area, as well as hire someone to come in and blow in some insulation to the entire area.


The key to insulation is to decrease the temperature differentials. Most of the time this is done by adding more insulation. With windows the ones that have a wider gap between the panes will do a better job than the one made for mobile homes (that are very close together).

Your plan should work as long as it increases the temperature differential.


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## hvaclover (Oct 2, 2008)

Where you been Marvin?

We got just the opposite here. Homes with boiler heat usually have ac equipment in the attic with large diffusers. We've run calls where uninsulated
ducts were connected to ceiling diffusers. The first year after these ac's were installed the HO would get water dripping from them--warm room air raising into the cold diffusers. 

Well, the HOs just got done paying company XYZ to install a new duct system but they would not come back to correct the problem either because the local code didn't heavily enforce insulated flex code in residential applications or no permit was pulled.

All we could do was advise the customer to cover the diffuser with plastic and tape a piece of one inch thick styrofoam to stop the infiltration of warm air.

Don't know what the out come was with that solution. Since they weren't paying for the right fix we would have to walk.

Can't put a bandaid on a bleeding artery.


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## Marvin Gardens (Sep 30, 2008)

hvaclover said:


> Where you been Marvin?
> 
> We got just the opposite here. Homes with boiler heat usually have ac equipment in the attic with large diffusers. We've run calls where uninsulated
> ducts were connected to ceiling diffusers. The first year after these ac's were installed the HO would get water dripping from them--warm room air raising into the cold diffusers.
> ...


All he wants is a bandaid for now. His plan should work to stop the dripping but will not cure the problem.

I think he understands this and doesn't want to take the time to make a permanent fix right now.

Plus I have been at the vacation home for 2 weeks...give me a break...I am just getting back and not in work mode yet...:yes:


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## meth (Apr 22, 2008)

Thanks guys - I understand that this is just a temporary band aid to get me through the current winter season, afterwards I will have a professional in to insulate the attic. Given the difficulty in accessing this area I am not sure if I will use blown in cellulose or spray foam. I can't see how anyone is going to get into there to work. Although I may wait until spring, remove some siding and cut a hole in the side for them to access and then patch it up. This area is above the garage so that poses others problems with heat loss. I am also heating the garage over the next couple of weeks so that will help with the bedroom above it.

The other section of the attic has both a/c units in it, with trusses across it that make it difficult to stand in front to even work on them - I will need to add some plywood to make a walking path to each, however the entire space is severely under insulatated. Since I may need to access this area to work on the units should I just re-do that area with batts and blown in for the areas I don't need to access?

My first spring projects are a new roof and re-insulating the attic


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## hvaclover (Oct 2, 2008)

Marvin Gardens said:


> All he wants is a bandaid for now. His plan should work to stop the dripping but will not cure the problem.
> 
> I think he understands this and doesn't want to take the time to make a permanent fix right now.
> 
> Plus I have been at the vacation home for 2 weeks...give me a break...I am just getting back and not in work mode yet...:yes:



I missed you dude.


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## Marvin Gardens (Sep 30, 2008)

hvaclover said:


> I missed you dude.


I hope you mean that in a platonic way....:laughing:

PC police are coming....run and hide...


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## hvaclover (Oct 2, 2008)

JJeez now you make me all embarrassed for coming from a Hellenic 
background



























































































































:laughing::laughing::laughing::laughing::laughing::laughing::laughing::laughing:

Got ya!!!


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## kbalut (Apr 6, 2009)

*insulating vents*

just wondering how this turns out. I have in floor heat so my A/C runs through our attic. We have flex tubes running down to the metal vents in the ceiling. the flex tube actually connects to a short one piece metal tube/vent which goes to the ceiling. This is the piece where the vent cover screws into. I have the condensation as well and have fought this for years. We ended up unscrewing the vent covers (we could reach), stuffing the vents with old towels and removing in the spring. I just can't imagine that this is what anyone would want to do. AND I can't even get to the vents at 15' up! so... last year, I army crawled through the attic and sprayed foam insulation around the vents. what a mess. not much luck there. I have had the attic inspected for more insulation, but I have plenty there. I did leave my ceiling fan on in the main room all winter to better circulate the air (towels still in the bedroom vents  ) this did seem to help. I was wondering if maybe those metal vents (the end part after the insulated flex tube) could be replaced with plastic vents... do they even make these? so, I'm VERY curious as well... permanent fix is needed desperately.


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## kenmac (Feb 26, 2009)

is the metal boot that the register mounts to insulated ?? I have seen plastic registers


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## beenthere (Oct 11, 2008)

The problem is natural convection currents are taking warm humid air into your duct system. Which is cold. And condenses that moisture.

Insulating around the register boxes helps, but doesn't eliminate the problem.

Try closing your returns off.

Also. good chance you have excessive duct leakage. Have them sealed, and that will also minimize the effect.


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## kbalut (Apr 6, 2009)

*vent issues*

My entire attic has blown in insulation... although the insulation dude said I had enough, I still did the army man crawl through the attic and sprayed the foam insulation around the vent boots. I do, by the way, close the vent returns. I understand WHY it's happening. I just can't figure out a great way to get it to stop. I do think leaving the ceiling fan on this winter helped (not the electric bill though). I believe the small amount of warm air gets through the closed vents, hits the cold boot and there you have it... condensation. remember... these vent covers are 15' up. Oh... I did try the lame magnetic covers... they don't stick well.

My final solution... paint and SELL


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## ablea (Aug 7, 2011)

I have a similar problem, but my ceiling vents are in my first floor ceiling so I am unable to get to them without tearing the ceiling out. Do any of you have any suggestions of how to tackle this problem?

Brett


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## beenthere (Oct 11, 2008)

Remove grille, and seal the cracks around the boot, then seal the grille to the ceiling.


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## kbalut (Apr 6, 2009)

I think I've solved my own problem. I believe the condensation was due to too much humidity...I shut down the humidifier and I no longer have the problem... I had to Kilz the brown stains around the vents and paint the ceilings


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## keithl1967 (Aug 14, 2011)

I have a very similar problem with vent condensation:

I have baseboard, oil fired heat that I put on when it is very cold outside, and a separate A/C- Heat pump that I turn off when the oil is on...

I have ONE vent that gets condensation and rips, and have absoluetly no access to the attic above to insulate it better.

It only seems to drip when VERY cold out, or when it snows (it's not a leak--no issues when it rains out!)

The vent is at the very end of the run, and is the furthest point possible away from the main unit.

I have a humidifier that I run upstairs during the winter, which I think may be contributing. 

Do you think running the fan on the A/C unit might help keep the air moving and stop the drip?


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## beenthere (Oct 11, 2008)

Its the room air going into the vent and cooling down that is causing the condensation. Just block off the vent.


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## kbalut (Apr 6, 2009)

*Vent Condensation*

My A/C guy did say I could run the A/C fan to circulate, but thought I'd just be cooling my house as air moved through the Attic venting. And I'd have to be careful to "catch" it in time. 

After my last post, I am now blocking the air flow. The magnetic flexible sheets available at some hardware stores DO NOT work as they don't stick well and don't really "close" the air duct. 

I now take the time (every fall) to unscrew the problem vents (only 3 have ever had problems…end of run) and stuff a towel in the duct. And screw the cover back on. It is a pain, but it works.


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## keithl1967 (Aug 14, 2011)

I have turned on the "circulator" fan, whihc runs at about 40% of the regular fan...

No more condensation drips now (for a week), and the house "feels" warmer (my humidifier is upstairs, not far from the A/C return...I think the circulator fan is moving the humidified air around the house much better now...


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## beenthere (Oct 11, 2008)

Might want to check inside the air handler to see if there is any condensation in it.


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## keithl1967 (Aug 14, 2011)

beenthere said:


> Might want to check inside the air handler to see if there is any condensation in it.


Thanks--hadn't thought of that...

The drip pan is bone dry...


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