Did a little poking around on Google but thought I'd also try the Pack for any experiences and causes/solutions before I call the contractor. 2 units in the attic, one with 9 drops and one with 14. Ceiling around the vents on the larger unit are clean for the most part but 2 of the 9 on the smaller unit are awful and the rest are clean. Seems odd that the set up and conditions are the same for all 23 vents but only 2 seem to be a problem. Some kind of leak in the trunks of the 2 or something else? Cleaned the ceiling around the 2 problem vents a year or so ago of what looked like dirt but now looking more like mold spores. House was built in Starkville a little over 5 years ago.
OT - Black Mold Around Ceiling Vents
- Thread starter MSUDOG24
- Start date
Do you have some gaps in insulation where the two problem vents are? If attic air can get around the vent it will cause condensation when it enters and meets the cold air from teh vent and the moisture will create a mold problem. Alternatively you could have some tears in your flexible duct going to the vent (or maybe some gaps where the flexible duct is tied into the main trunk) so you have the same problem that starts a little further back. If that's the problem, you likely have mold in your ductwork also .
If your ducts have leaks that let in warm air, this temperature differential can cause the same kind of problem. The difference between the cold air in the ducts and warm air in the attic can cause moisture to condense on the ducts, giving mold a perfect environment to grow.
You can take off the grill and see if you feel any warm air where the duct meets the drywall ceiling. If yes you could caulk any gaps between the drywall and the duct. You're probably need to get in the attic and seal where the duct meets the drywall with a can of spray foam, foil tape on the duct joint if it's leaking, additional insulation or all three.
A $12 non contact thermometer from harbor freight may help finding the source of the hot or cold air leakage causing the problem.
You can take off the grill and see if you feel any warm air where the duct meets the drywall ceiling. If yes you could caulk any gaps between the drywall and the duct. You're probably need to get in the attic and seal where the duct meets the drywall with a can of spray foam, foil tape on the duct joint if it's leaking, additional insulation or all three.
A $12 non contact thermometer from harbor freight may help finding the source of the hot or cold air leakage causing the problem.
Lots of things could cause that, leaky duct like you said, poor insulation or air sealing in the ceiling by the register, or an uneven airflow situation.
I had a sharp guy explain to me that AC's are also dehumidifiers and the reason you don't want one to be oversized is it will cool too fast and cut off before it has the chance to dehumidify the air. I would assume that is not an issue since the house is new construction, it was hopefully sized properly.
Do you have one centralized return for the system in question or returns in every room? If it's centralized and the registers getting mold are behind closed doors, it could be that the air isn't circulating. I had a unit replaced about 5 years ago and they explained this to me and talked me into spending a few hundred extra bucks to add a return to all of the bedrooms and boy it was a game changer. The house became way more balanced in temp instead of the variations in temps in the bedrooms I always blamed on being on the "sunny side" of the house.
If you don't have one, you can pickup an infrared thermometer for $25 or so on amazon. With the ac off you can shoot the ceiling around all your registers and if the two getting mold are hotter/colder than the others, you likely have an airsealing/insulation issue. You can also see if those 2 registers are just blowing colder/warmer air when it's cut on.
That's all I have for you. There are some professional HVAC guys on the board that can probably tell you a lot more.
As an ETA. I am getting a whole house ductless mini split system installed on Thursday and I am geeked about it.
2nd eta. Looks like everyone of us know-it-alls want you to check that ceiling temp around the registers, lol.
I had a sharp guy explain to me that AC's are also dehumidifiers and the reason you don't want one to be oversized is it will cool too fast and cut off before it has the chance to dehumidify the air. I would assume that is not an issue since the house is new construction, it was hopefully sized properly.
Do you have one centralized return for the system in question or returns in every room? If it's centralized and the registers getting mold are behind closed doors, it could be that the air isn't circulating. I had a unit replaced about 5 years ago and they explained this to me and talked me into spending a few hundred extra bucks to add a return to all of the bedrooms and boy it was a game changer. The house became way more balanced in temp instead of the variations in temps in the bedrooms I always blamed on being on the "sunny side" of the house.
If you don't have one, you can pickup an infrared thermometer for $25 or so on amazon. With the ac off you can shoot the ceiling around all your registers and if the two getting mold are hotter/colder than the others, you likely have an airsealing/insulation issue. You can also see if those 2 registers are just blowing colder/warmer air when it's cut on.
That's all I have for you. There are some professional HVAC guys on the board that can probably tell you a lot more.
As an ETA. I am getting a whole house ductless mini split system installed on Thursday and I am geeked about it.
2nd eta. Looks like everyone of us know-it-alls want you to check that ceiling temp around the registers, lol.
Last edited:
I know this will sound nuts but it’s true. I had a house with a vaulted ceiling. Two vents had mold and dropped condensation. The grill was on upside down the cool air came out pointed up. Cool air falls so it rolled back on itself and caused the condensation and mold. Reversed them to point down and no more problem. ETA hated that house and sold after 2 years
Like a few have suggested it's condensation due to poor insulation around the vent boot. When its cool in the attic wrap that guy as good as you can with insulation on the outside in the attic. It will also help to caulk around the inside of the box to prevent any warm air getting in. Hell even use spray flex seal.
I run a HVAC business in Madison - usually get 2-3 calls a week about this. All this rain doesn't help either because it increases the humidity in the house and makes it more likely to sweat.
Latest posts
-
Debbie Downer football question...
- Latest: drexeldog23
-
Better late than never NSFW
- Latest: TXDawg.sixpack
Get unlimited access today.