# condensation coming out of air vent



## bmancanfly (Mar 3, 2009)

I've got condensation coming out of my A/C vents. The duct work is in the attic.

Not sure how long this has been going on (it's a rental property) but there is quite a bit at some vents, not so much at others. 

Any suggestions on what the cause might be and how to resolve it myself would be appreciated. Money is kinda tight right now and if it's something simple I can fix without calling a service tech would be great.


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## Plumber101 (Feb 25, 2009)

Sounds like the duct work is not insulated.

All duct work in an attic needs to be insulated to include the pleum, trunk and branch ducts


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## bluefitness (Sep 4, 2008)

bmancanfly said:


> I've got condensation coming out of my A/C vents. The duct work is in the attic.
> 
> Not sure how long this has been going on (it's a rental property) but there is quite a bit at some vents, not so much at others.
> 
> Any suggestions on what the cause might be and how to resolve it myself would be appreciated. Money is kinda tight right now and if it's something simple I can fix without calling a service tech would be great.


If the vents are condensating, you check for an air flow restriction. I'm guessing the filter is blocked. I would start there. It could also be a dirt evaporator coil.


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## Plumber101 (Feb 25, 2009)

bluefitness said:


> If the vents are condensating, you check for an air flow restriction. I'm guessing the filter is blocked. I would start there. It could also be a dirt evaporator coil.


 
If the coil is freezing because of a lack of air flow then normally the complaint from the HO is the house is hot. See freezing not condensating.

Duct in attic..attic hot..no insulation..duct cool...then condensation on/in duct and out of vents..

I have thawed many coils and NEVER a complaint that there is water coming out the vents

Went on a big job the other day where the main trunk went through and office and into the warehouse..Not insulated and when people walked through the door to the warehouse the would be dripped on. Insulated duct problem fixed.

Start with the duct


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## bluefitness (Sep 4, 2008)

Plumber101 said:


> If the coil is freezing because of a lack of air flow then normally the complaint from the HO is the house is hot. See freezing not condensating.
> 
> Duct in attic..attic hot..no insulation..duct cool...then condensation on/in duct and out of vents..
> 
> ...



I'm not saying that it has gotten to the point that the coil is icing. When the air flow slows down enough, the air coming out of the registers drops the register temperature below the dew point. This causes condensation on the vents. Think about it. If you have a cold glass of water, you will see condensation on the outside of the glass. When air flow is restricted, it will cause the metal of the register to become too cold. What do you get? Condensation. Check your filters before going to deep into it. 

Trust me. It will cause condensation.


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## bmancanfly (Mar 3, 2009)

Well, I went up in the attic and much to my surprise the plenum, and all ducts are well insulated.

Also checked the air filter and it is not clogged, or even particularly dirty.


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## JohnH1 (Jan 9, 2009)

Remove one on the vents that are dripping and see if the boot has a tight fit around the drywall or is there some space were the attic air can mix in. it should be a tight sealed fit.


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## beenthere (Oct 11, 2008)

JohnH1 said:


> Remove one on the vents that are dripping and see if the boot has a tight fit around the drywall or is there some space were the attic air can mix in. it should be a tight sealed fit.


Yep.

Good chance your drawing attic air in.

Seal the boots to the opening in the ceiling.


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