Help with condensation in duct work

[stumped56]

Is there anybody out there who can get me in the right direction to have this severe problem corrected? I had my central A/C professionally installed, or so I thought. I have had nothing but problems, with condensation collecting in the ducts that are located in my cold air attic over the winter months. I am ready to have the whole darn thing ripped out. Just ask and I will let you know this supposedly respectable company. Thanks.

[badboyheel]

do you know if the ductwork is insulated? duct must always be insulated in unconditioned spaces, i usually use at least an r 7.

[bluetooth751]

Calm down buddy. you have a problem many people see in colder climates or even warm climates.

Warm air is rising and entering your duct work from your conditioned space. That warm humid air is condensing in your cold duct work.

Give us more info and we can easily help you correct this problem.Simply running your fan on continuous can reduce the amount of condensation.

[t527ed]

running the fan on low speed with a timer will eliminate the problem if ducts are insulated. only other option would be sealing all registers for the winter. this is a very common problem for air only attic systems.

[stumped56]

Hey Thanks for the quick responses! Yes the ducts are insulated. Not sure of the r value. There is a main steel trunk with the 6" & 7" insulated flex with the alum. exterior. I looked into a variable speed fan so I can run it at a constant low speed with out the feeling of a cold breeze in the house. I figured it will help filter the air in the colder months. There is also an Aprilaire 2200 filter that collects the condensation like crazy. I have some pic's. If i find out how to post them I will. I was also looking in to airtight registers with no luck. I contacted the contractor and at first they said they would help, then quickly reneged on their offer to help. Sorry to sound bitter . I know there are a lot of excellent installers , I just feel like I got stiffed. I even purchased a Hygro-Thermometer to monitor the humidity in the house. Thanks.

[teddy bear]

What was the %RH in your home this winter? What is climatic zone? Operating the fan periodicaly to warm the inside surface of the duct and evaporate any moisture in the duct is the best answer. Many homes are so dry that this is not problem. That dry is not comfortable. Regards TB

[beenthere]

As bluetooth pointed ouot. Warm air going into duct that is below the dewpoint of teh warm air, is the problem.
Stop the air flow into the duct, and you will stop the condensation.
Running the fan in winter when your duct is in the attic, adds to the heating bill.

[21degrees]

I can't believe they are still putting furnaces in attics in colder climates, you are asking for trouble. The insulation better be at least 2" thick. I once ran spiral duct in attic and insulated with 1' insulation and had to go back and throw 1 more layer and have hime continously run his fan. As far as flex for run outs you should not use unless you don't care about end results. Laminar flow is better and quieter.
Hey Thanks for the quick responses! Yes the ducts are insulated. Not sure of the r value. There is a main steel trunk with the 6" & 7" insulated flex with the alum. exterior. I looked into a variable speed fan so I can run it at a constant low speed with out the feeling of a cold breeze in the house. I figured it will help filter the air in the colder months. There is also an Aprilaire 2200 filter that collects the condensation like crazy. I have some pic's. If i find out how to post them I will. I was also looking in to airtight registers with no luck. I contacted the contractor and at first they said they would help, then quickly reneged on their offer to help. Sorry to sound bitter . I know there are a lot of excellent installers , I just feel like I got stiffed. I even purchased a Hygro-Thermometer to monitor the humidity in the house. Thanks.

[t527ed]

I can't believe they are still putting furnaces in attics in colder climates, you are asking for trouble. The insulation better be at least 2" thick. I once ran spiral duct in attic and insulated with 1' insulation and had to go back and throw 1 more layer and have hime continously run his fan. As far as flex for run outs you should not use unless you don't care about end results. Laminar flow is better and quieter.



if the furnace was in the attic the OP would not have a condensation problem........;)

[beenthere]

if the furnace was in the attic the OP would not have a condensation problem........;)
I'm not sure about that on a tight house. Could have a long enough off cycle, that with the fan running 24/7, the return could have condensate.

I don't recall having any customers that ran their fan 24/7 with an attic install though.

[t527ed]

I'm not sure about that on a tight house. Could have a long enough off cycle, that with the fan running 24/7, the return could have condensate.

I don't recall having any customers that ran their fan 24/7 with an attic install though.



ok:rolleyes:...;)





even with the fan running 24/7 wouldn't the moving air prevent the condensation?:confused:

[beenthere]

I guess that would depend, on how much insulation the duct has, what the velocity of the air is, what the temp in the attic is, and the dewpoint of the return air going into the attic duct is.

At 70*F, 35%RH, the dew point is 40*F. So if those are his indoor conditions, and the internal surface temps of his duct and air cleaner are at or below 40*F, it can and will condense with the fan running 24/7.

I don't know what his attic temp is though, or any other pertenant info about his house and system.

As more and more houses have their insulation increased(R38+), I think it will become more of a problem though.

[21degrees]

Our attic temperature can get 35 F and we have had condensate form in ducts. The house temp would be 70 to 72 F ther is a big temp variance. I know it is common in the states but it is not common here in canada. We found that this house was very tight R2000 home.You can wipe it with your hand
I guess that would depend, on how much insulation the duct has, what the velocity of the air is, what the temp in the attic is, and the dewpoint of the return air going into the attic duct is.

At 70*F, 35%RH, the dew point is 40*F. So if those are his indoor conditions, and the internal surface temps of his duct and air cleaner are at or below 40*F, it can and will condense with the fan running 24/7.

I don't know what his attic temp is though, or any other pertenant info about his house and system.

As more and more houses have their insulation increased(R38+), I think it will become more of a problem though.

[21degrees]

Canadian climates are alittle bit different than in NJ. The Trap would freeze on high efficiency. I just did a addition above a garage with infloor heating and glycol was tested for minus -28 C at a testing facillaty and loop still froze. Have not seen one here and don't plan on being the first.
if the furnace was in the attic the OP would not have a condensation problem........;)

[stumped56]

RH has been between 30 - 35% in the winter. Yes, I have added to the existing attic insulation it is around 8" currently from the 3" when we moved in. I have even wrapped the A/H with blankets of r-19 to help keep the temp. up. I"ve thought about putting a type of hot water coil in the system to work in conjunction with my baseboard hot water. Am I going in the absolute wrong direction?

[t527ed]

Canadian climates are alittle bit different than in NJ. The Trap would freeze on high efficiency. I just did a addition above a garage with infloor heating and glycol was tested for minus -28 C at a testing facillaty and loop still froze. Have not seen one here and don't plan on being the first.


i would never put a 90+ furnace in an attic in that artic wasteland of yours...:D


i have been doing them in nj since around 1984 or so and have never had a problem.

[beenthere]

Stumped. Once you get the moisture out.
Block off the return, and supply regs. If air can't get in, then it won't be moisture to condensate.

[21degrees]

You have not even been here and you call it waste land. Sounds like thats your answer. NJ is a waste land compared to where I am. The reason you put them in attics to lazy to put them where they belong and can be serviced properly. Try visiting sometime just leave attitude behind.
i would never put a 90+ furnace in an attic in that artic wasteland of yours...:D


i have been doing them in nj since around 1984 or so and have never had a problem.

[t527ed]

;)
You have not even been here and you call it waste land. Sounds like thats your answer. NJ is a waste land compared to where I am. The reason you put them in attics to lazy to put them where they belong and can be serviced properly. Try visiting sometime just leave attitude behind.


been to canada 3 times, nice place to visit wouldn't want to live there.:rolleyes:


the :D after the artic wasteland means i'm kiddin you.

some houses around here the attic is all we get to work with, we don't design or build them. we just heat and cool them.

[21degrees]

Sorry, I thought you were calling me an eskimo. I would actually like to see how you guys do your Installs. We put furnaces mainly in basement, closets and crawl spaces. But I have not seen any in the attic yet. Hate crawl spaces and Attics. Sometimes we have to run wire up to attic and then back down due to finish basements. HRV exhaust ducting is now going in attics and has to minumum 1.5" Insulation, with foil taped joints for moister or inspector calls us on it everytime.

[t527ed]

most of ours are basements, some crawls, one whole town with counterflows on slabs and units are in laundry room or closet in the garage.

last house i was in i had a pulse furnace in attic because i did not want to lose headroom in basement that i ended up finishing.

attics are becoming more common over the years and i would rather be in an attic than a muddy crawl space. i just don't go into the attics anymore on a hot day.....;)

[21degrees]

are you codes very stringent. We have to have access and customers has to be able to access without need of any tools including ladders. Even on commercial we do not carry ladders they are all fixed to structure. You are not allowed to have filter rack that requires screw driver. These guys here a nuts. If you don't have clearances you will get called. We have to pull permits on all retros
attics are becoming more common over the years and i would rather be in an attic than a muddy crawl space. i just don't go into the attics anymore on a hot day.....;)[/QUOTE]

[coolmen]

most of ours are basements, some crawls, one whole town with counterflows on slabs and units are in laundry room or closet in the garage.

last house i was in i had a pulse furnace in attic because i did not want to lose headroom in basement that i ended up finishing.

attics are becoming more common over the years and i would rather be in an attic than a muddy crawl space. i just don't go into the attics anymore on a hot day.....;)
Been installing in attics all the time with no issues. homeowners want as much square ft as possible in the zillion doller homes. Pulse in the attic can be noisey due to the weight of the thing along with the pulsing.

[t527ed]

Been installing in attics all the time with no issues. homeowners want as much square ft as possible in the zillion doller homes. Pulse in the attic can be noisey due to the weight of the thing along with the pulsing.


i could here it if i listened for it, house was a ranch and it was over the living room.