Air Conditioning - Central AC Condensation in Ducts/Flex Pipe

Hello,


Has anyone ever experienced condensation in your AC vents/ducts/flex piping?

I live in a ranch and have all the duct work/Air handler in the attic. I have the blown in insulation with a ridge and soffit vents. I only experience condensation issues in the winter.

I have been told many things to do.... The only thing that seems to help is to run the AC FAN periodically during the day. Said it should dry out the ducts/vents... I also bought a dehumidifier for the basement. It seems like that helped...

Could the moisture be coming from the basement causing the condensation in the ducts?

Has anyone else experienced this? Any remedies? etc?

Thank you!

Is the ductwork properly supported? At home inspections in my climate (Chicago) you can see condensation when flex duct insulation is compressed by hangers, or by laying on the attic or crawlspace floor, or where it crosses trusses, etc. - when compressed, the "R" value reduced. This also sometimes happens when installers wrap insulation over-tightly to produce a "neat" job.

For basic primers on duct installation and reducing AC duct condensation see:

http://www.contractingbusiness.com/25/ServiceClinic/Article/False/46151/ServiceClinic
http://www.contractingbusiness.com/25/ServiceClinic/Article/False/6141/ServiceClinic

If you do not have heat on this unit which it sounds like you do not the only way I know of is to run the fan. I think ED might have some info for you. He should be along soon.

If you do not have heat on this unit which it sounds like you do not the only way I know of is to run the fan. I think ED might have some info for you. He should be along soon.

Thanks Airman....

It seems like that is doing thr trick... and honestly, after adding the dehimidifier in the basement, it seems like it has taken the humidity out, even upstairs... Could that play into it? Too much humidity or am I thinking too much?

Also, someone mentioned about wrapping the duct for more insulation... not the flex, the duct... Could that help?

First is that just a AC in the attic???????? or does it have heat also???? What heats the home ??? If you have hot water heat in the home and the AC in the attic This will happen. close all the dampers at the registers tight. If this dont do it . Fill plastic bags with paper and pull the registers off put them in the pipe and put the registers back on. Put a 4 mil-poly over the return grill. This is to stop the warm hum air from going up into the pipe and get cold then let the water out of it.;) ;)

First is that just a AC in the attic???????? or does it have heat also???? What heats the home ??? If you have hot water heat in the home and the AC in the attic This will happen. close all the dampers at the registers tight. If this dont do it . Fill plastic bags with paper and pull the registers off put them in the pipe and put the registers back on. Put a 4 mil-poly over the return grill. This is to stop the warm hum air from going up into the pipe and get cold then let the water out of it.;) ;)

That is exactly what I have.... Gas, hot water baseboard.

Ed, I tried closing registers, etc and that seemed to make it worse.

It seems with the dehumidifier running in the basement and running the fan a few times for a few minutes during the day seems to have worked. I am a 'warm' person and running the fan seems like it circulates the dry/stale air....

That is exactly what I have.... Gas, hot water baseboard.

Ed, I tried closing registers, etc and that seemed to make it worse.

Then like I said you have to plug the registers so that warm hum air cant get back up in to the pipe and duct up in the attic. To cool down . That is where the water comes from

Then like I said you have to plug the registers so that warm hum air cant get back up in to the pipe and duct up in the attic. To cool down . That is where the water comes from

That seemed not to work...

i don't mind running the fan once or twice a day... Seems like it circulates the old/stale air. I am a 'warm' person and running the fan when we have a lot of people over, seems to cool things off. i have had less condenstation then i have had in the past. Someone recommended to put more insulation/wrap the duct. Can this help?

Like I have found of the years. You have to fix it so no warm moist air from in the home. Cant get back up in the duct work there in the attic.

What Ed is suggesting is that just closing the registers is not good enough. You would need to SEAL all the registers by taping plastic sheeting over them. Not very attractive in my mind.

If the A/C air handler has a multiple (or variable) speed blower motor then I would install a timer to run it on the lowest speed several times a day.

Thanks for the excellent links!

On this condensation problem, I'm having all my flex duct replaced. I cut into one of the ducts that was water logged and in your worst nightmare you would not want to see what I saw in that duct. Also, the plenum actually had standing water in it. That's being replaced also. The new plenum will be constructed of duct board. Anyone out there have any experience with that? I've heard good and bad about duct board plenums. I'm looking at getting away from the metal. Also, I'm having the optional heating element installed in the air handler/coil unit, thus converting it to a furnace, something I opted not to do when it was originally installed. Pushing warm air through those ducts should keep them dryed out. Or am I missing something here. Anyone out there who has been thru this, speak up. I want to hear from you.

Duct board will break down over time releasing fiberglass into the air. Plus it will grow mold easer thwn metal.