AC Vent mildew??

[chrigging]

Why would only one AC vent mildew? This is in a new house, with a new AC...
All the other vents look fine. The vent that is the issue is the guest bathroom if that makes any difference.

[ken]

It could be there is more humidity in that bathroom causing condensation on the register that eventually feeds mildew. Is that bathroom used a lot for showers? It could also be this register puts out colder air than the rest of the house, resulting in more condensation

[BertramBass]

How often is the bathroom used? Is the exhaust fan used? Is the door kept shut? Any windows? Lots of condensation?

[chrigging]

How often is the bathroom used? Is the exhaust fan used? Is the door kept shut? Any windows? Lots of condensation?

The shower is used daily.
No fart fan, the door is shut only when in use...
Yes one window, not near the vent..
No visible condensation, just mildew spots.
I took the vent down, soaked in bleach, and repainted it over the weekend.
I noticed new spots developing this am.

[BertramBass]

A new house with no exhaust fan in the bathroom? I would start right there if it is used daily...

[MisterB]

Need exhaust fan. You might put an ozonics in there for 24 hrs with the room closed up.

[double bogey]

It is due to high humidity in the bathroom. Supply air temp is lower than the dew point, causing moisture to condense on the grille. Bathrooms with windows are not required to have an exhaust fan. Is there any way to open the window a bit? Common issue, got to get moisture out of the room after you use the shower.

[JBT]

go up in the attic and make sure the vent is insulated all around where it connects to the ceiling - I had the same issue in our master bedroom and the blown in insulation had been moved away from the vent and i could see exposed drywall, i placed insulation back all around and bleached vent and never had the issue again

[Throwin Darts]

tagged

[Briar Friar]

It is due to high humidity in the bathroom. Supply air temp is lower than the dew point, causing moisture to condense on the grille. Bathrooms with windows are not required to have an exhaust fan. Is there any way to open the window a bit? Common issue, got to get moisture out of the room after you use the shower.

Yes. Unfortunately nobody likes to open the window...hot air comes in during summer....cold air comes in during winter. At my rental houses that have this issue...I hardwire a fartfan/vent fan to the light switch...so...any time the light is turned on...the fan comes on. It has resolved alot of m/m issues and drywall tape popping and texture peeling. Those will be your next issue if not resolved as prescribed.

I use a vinegar and bleach mixture in a spray bottle to combat m/m. I mix it hot...20% or more....of both bleach and white vinegar.