ductwork in attic condensing

[Deleted User]

I work for a good size oil company in the northeast.Over the past few years we started getting into the A/C side of the industry.We install Acoils in furnaces and many new complete attic jobs.Recently we have gotten calls from customers stating there is water coming from the difussers.Iam trying to figure out a way to make the ductwork stop forming moisture inside.My supplier suggestsputting magnetic covers over the difusser,but I thought there must be a better way.Any ideas would be appreciated thanks in advance

jim lockard

water

how are you insulating the duct work ?

Justin Gavin

Time to plug it

You have 2 options, plug the hole and plug the hole.
The the bottom line is you have to stop the heat from entering the ducts that causes condensation. I live up in Green Bay Wisconsin and I am sure the weather is similar to what you experience over there.

I know it might look cheezy but you really have no other choice.

We do alot of High Velocity AC installs and the diffusers come with a plug that comes in handy.

Good Luck

[Deleted User]

We are wrapping the trunk line in fiberglass duct insulation,and the branches are usually flex duct.

Don_4

water

To understand why the water forms you need to know where the water is coming from. Warm moist air from inside the house is contacting a cold metal pipe in the attic which causes it to condense and form water droplets. The only two methods of controlling it are; stop the air from entering the duct or better insulation on the ducts to keep them warmer. I live in Winnipeg, Canada, this is a very normal problem here. I usually use at least 2" of insulation around the pipes along the run and even more where it is close to the ceiling.

Andy_6

The simple fact about the water in the attic ducts is the air from the house is hitting its dew point in the duct work. Simply turn the fan to the on position to evaporate the water and run the fan peridocally to keep the moisture out of the ducts.

Mark Hunt

That won't work

> The simple fact about the water in the attic

> ducts is the air from the house is hitting its

> dew point in the duct work. Simply turn the fan

> to the on position to evaporate the water and run

> the fan peridocally to keep the moisture out of

> the ducts.





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Mark Hunt

That won't work


You need to stop the air.

Code requires R-8 insulation for ducts in unconditioned spaces. Even that will not stop the condensation.

I would suggest you seal the registers with shrink wrap in the fall.

That is the only way I know of to stop air migration into the ductwork.

Mark H

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Randy Berg_2

I have learned about this the hard way. What I do now is insulate the inside of the duckwork and also wrap the outside with duct wrap as well. Even with this we still have had problems, then we will seal or close off all the supply and return grills. We also try and keep the flex duct to a min. or use all hard duct. We might lose several new jobs because of the added cost of doing this but it beats gettings calls in the winter of water dripping from grills ect. Good Luck

Big Ed

Also Check

The humidifier settings. Most leave it at 35% but you need to drop it as the outside temp drops colder. I like the humidifires with the outdoor sensor...

GaryDidier

Water

Mike,
It doesnt mater how much insulation is installed on the ductwork and piping.The insulation only helps when the system is running to help delivery efficiency. Insulation is misunderstood in that it actually slows down heat loss or gain, not stop it as some might think. The piping in an unheated space will eventually cool to the dew point and will produce condensate no matter how much insulation is on it.The colder the climate, the worse the problem. Running the blower would only help if it were run long enough to keep the inside of the system above dew point.This would cause uncomfortable cold blowing air. It seems the only practicle solution is tightly sealing the system to air entry. Then I wonder if mold within the system will also become a problem!!
Gary from Granville

Climate Creator

Here in CT......

We don't really see that problem, people don't have to wrap or seal the ductwork. But I did have this problem once, where the people had a boiler and a separate a/c system in the attic. what was causing water to drip from registers in other rooms was humidity from the shower, watch for supplies in the bathroom, and obviously never put a return there. The reason it would drip out of certain ones is that when it would condense, just like steam it returned via pitch, and some of the runs pitched just right to "return" condensate to different rooms. We eliminated the register in the bathroom and solved the drip. The mold left in the ductwork after that was a different story, don't forget to check for that nasty stuff!!!

Hope this helps,
Rich

Dave_16

condensation from registers

I've run into this problem a few times and normally only when the duct is wrapped and not lined and evenmore so when the registers are on the outside wall, I don't care if they are metal boxes or 1 piece plastic, especially when the eaves are totally vented, it does'nt matter whether you shut the grill or not, if the diffussers are on the outside wall this problem is likely to occur. insulate HEAVILY AROUND THE BOX AND MAKE SURE YOU BLOCK THE EAVE VENTS WITH INSUlATION, and as was stated in another post have the home owner run the fan only a few hours a day

Mark J Strawcutter

ice dam

Do NOT block the eave vents, or you're trading one problem for another. Ice damming at the eaves is caused by a combination of insufficient insulation and insufficient ventilation.

By blocking the vents you trap any heat that makes it up into the attic, causing snow melt then water runs down roof and freezes at cold eaves.

Mark

Dan M

Blocking eave vents is hard on shingles

Blocking eave vents can lead to shingle curling from over heating

Dave_23

Condensation in A/C attic ductwork

I recently installed a Spacepak system in my steam-heated home. My Spacepak has 18 outlets (diffusers) and 1 warm air return. Bottom line on stopping condensation is to plug each diffuser and it convenient, the warm air return. Moist, warm air from indoors will circulate by convection through the system. The warm air will be cooled by the attic ductwork, which will condense its moistureon the surfaces of the ductwork. This will lead to dripping or mold problems, or both. Protect your investment and health - at least plug the outlets with the stock plugs. Note: To avoid using a ladder on higher outlet, I use an old piece of 1 inch pvc to place the plugs. Use the same pipe to knock them out before the cooling season begins. They're not that tight of a fit, but they are very effective at stopping the convection airflow.

Dave_23

High Velocity A/C ductwork condensation

I recently installed a Spacepak system in my steam-heated home. My Spacepak has 18 outlets (diffusers) and 1 warm air return. Bottom line on stopping condensation is to plug each diffuser and it convenient, the warm air return. Moist, warm air from indoors will circulate by convection through the system. The warm air will be cooled by the attic ductwork, which will condense its moistureon the surfaces of the ductwork. This will lead to dripping or mold problems, or both. Protect your investment and health - at least plug the outlets with the stock plugs. Note: To avoid using a ladder on higher outlet, I use an old piece of 1 inch pvc to place the plugs. Use the same pipe to knock them out before the cooling season begins. They're not that tight of a fit, but they are very effective at stopping the convection airflow.

Dave_23

During the Summer

It's interesting to note that the reverse will happen in the Summer. The cool ductwork in the hot, moist attic will condense moisture externally on the duct runs. This isn't nearly the problem internal condensation may cause during the Winter months, if the diffusers aren't plugged. During the Winter, repeated internal condensation = ruined ducts, mold and water damage.