Air Conditioning ducts leaking in winter.

Ed_13

Hi,

I know that this site is primarily for wet heads, but I think that this is where all the
“Smart People” are (Smile), so I thought I would try here first.

This year I have seen an abnormally high number of central A/C systems in very cold and well ventilated attics condensing on the interior of the ducts, and leaking water into the home.

In some of these homes the homeowners have sealed the return ducts and put magnetic seals on all of the delivery ducts to stop air flow, and the problem persisted.

I have heard this described in the past a “thermal siphon”. There are also probably other terms used to describe the condition. The problem occurs when the warm moist air in the home flows into the A/C ducts and creates a siphoning effect, where by the warm air rises and enters the A/C duct and the cool air falls out a different duct.

The moisture in the warm air condenses inside the ducts and fills them with water that freezes. When the weather gets warmer the ice melts and the water leaks down through the ceiling.

I generally understand how it is caused. However, when you tell a homeowner about the problem they are skeptical because “their neighbors have the same A/C system and they do not have the problem”.

I am looking for some web sites and or publications that I can refer to when describing the problem to people. It seems that when you tell someone something, they roll their eyes. However, when they read in on the web, from another source, they then will believe it.

Any links to sites that address the problem of condensation forming inside the dormant A/C ducts in the winter, and suggest solutions for the problem, would be greatly appreciated.

Best Regards
Ed Carey

brent_3

I know the situation well. It's interesting that some homes have the problem and some don't. I think a lot of it has to do with how humid the room air is. Most duct is only about R-4 so it doesn't take much. I think those that have the problem with water dripping usually try to seal the registers. In my house I let the registers open and i don't have a problem. Yes, I do feel cold air falling out of the registers. If the registers are open I think the warm air flows up and the cold drops down and nothing condensates. If you try to seal them, warm moist air slowly leaks into the ducts and condensates.

just my opinion

Brent

mellow

duct

The ducts just five years back had very little insolation. The code changed around here and we had to use better insolated ducts. If it was me I would say the more you insolate the better. The inside of the duct compared to the atic has the most delta T in the house. They can close the vents in winter too. this will also help.