Condensation from Ceiling AC Vent

meth

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?

kennzz05

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

meth

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.

Marvin Gardens

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

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

Marvin Gardens

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

Sounds like an easy fix - Thanks!

Marvin Gardens

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

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kennzz05

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

meth

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.

Marvin Gardens

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

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

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...

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meth

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

hvaclover

I missed you dude.

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