Condensation on A/C Vent

[kate2689]

What would cause (a lot) of condensation to build up on the vent in my 2nd story bathroom. The house is 5 years old and prior to a few months ago did not do it. The attic is very hot (we live in the South) and the a/c comes on frequently, but none of the other rooms in the house have this problem. It is getting worse - the whole area smells like mildew/mold and I'm starting to get concerned. The bathroom is rarely used and there is a window, which I keep closed because of the heat/humidity outside. HELP, I can't stand the smell.
Kate

[16x80]

kate2689

Welcome to Home Repair Forums

Condensation is caused by bare metal in a hot space when cold air is moved thru it! In short you need to get into the attic and check that run to make sure there is no bare metal showing. Typically it should have been run in an insulated flex duct that has an R value on 4.5. I have seen in some installations that the HVAC guys did not cover the Boot that connects to your room with insulation and have seen moisture on the register, But the way you talk it sounds like you may have more showing than just that. Also I would look for sags in the run, Sags may have standing water in them that would cause a mold growth. Best way to remedy this if you find a sag in the run that is holding moisture is to drain it and then provide proper support for the run.


Very interested in what you find out, Please come back and post your findings for me.

16x80

[Todd]

Will limited air flow at the vent cause condensation? I have a contract on a house and in the basement playroom the ducts seem to be fine but at the vent there is mildew and condensation. A friend of mine that is in the real estate business( buys houses fixes and then sells)said to put in a bigger vent.

T

[16x80]

Air flow is a tough one to explain.

A house is sized for a certain amount of heat gain heat loss then the proper equipment is installed.
Each room has a specific amount of cfm that needs to be supplied to properly condition the air.
Air follows the path of least resistance!
Its hard to push air, but its not hard to pull air.
If you over size the run to the room you would lose supply from somewhere else.
If you have a supply in a room with no return you would then load the room, Air is forced to be pushed in with no return.

Todd you could pull a return from that room back to the furnace and increase the flow with out robbing from the rest of the house.

16x80

[Todd]

Thanks 16x80, I'll try it if we close on the house and I'll let you know the results.

T

[DougChemist]

No sweat

I imagine that the 2nd floor bathroom is where you generally shower. It's therefore the most humid room in the house and that's why you get condenstation there. Run a ventillation fan when you shower and you shouldn't have any more problems.

[hvacwiz]

I imagine that the 2nd floor bathroom is where you generally shower. It's therefore the most humid room in the house and that's why you get condenstation there. Run a ventillation fan when you shower and you shouldn't have any more problems.

Ummm.......post is 7 years old, I'm sure the problem has been dealt with by now.