Mold Ghosting Growth on Tray Ceiling
Hoping for further insight into some mold growth that appears on my tray ceiling during the humid July/August months we have here. Land is clay and near a river so while the lot drains, with heavy rains it can also be very wet.
Background: House is 23 years old. About 20 years ago I added on a 900 SF Master Suite Addition. The problem with mold growth on the addition ceiling did not appear for many years…probably appearing about 5 or 6 years ago. There is no mold growth in the original footprint of the house. I have 3 HVAC units for the house. The addition has it's own separate one.
Ceilings: The ceiling in the bedroom is a 14 foot tray and the bedroom is 25 by 18 feet. The ceilings in a small hallway with adjoining his and her closets are 9 feet. Most of the ceiling in the adjoining bathroom is 9 feet but there is also a steep cathedral ceiling in a small portion over the corner tub. A new hallway and powder bathroom were added into this addition. Then it all connects to the original house.
The Bedroom tray has a row of slanted recessed lights on both parts of the ceiling that slant towards the flat top of the tray.
Mold: Appears this time of year. It is more like ghosting mold rather than black stuff. In years past, confused by this I have gotten out my clorox solution, sprayed with Benefect and in some cases repainted the ceiling with Zinsers Bulls Eye (that has worked in the powder room).
Powder Room: Last year after I cleaned with Clorox and Benefect and painted with Zinsers, I saw water dripping from the ceiling and moldings. The exhaust fan was allowing hot air from an unvented attic space to seep into the room. So…I duct taped the openings in the exhaust fan to test…and no condensation. Problem identified. (1) exhaust fan not vented to roof and (2) that portion of the roof was not vented. Last week, I put a static vent in this portion of the roof (was waiting on my brother but finally had someone else do it) I still have the exhaust fan duct taped and will keep it there until it can be vented thru the roof. But…there was no mold growth in this room this year. Hurrah!
Last year, I conditioned my crawl space in hopes of keeping moisture problems from the land from being a factor. It was not cheap to do this.
But mold growth appeared on ceilings where it had never appeared before. Specifically the hallway with the closets (no mold in closets) and the bathroom ceiling both the 9th foot part and the cathedral part. And again some ghosting on the bedroom 14 foot tray. After looking at the architectural drawings, I realized the builder did not put in the gable vents. He put in only 2 static vents. This was a large addition, with a large roof system. So also last week, I had a power vent put in on this roof (the attic is already much cooler). At my brothers suggestion, we sealed off the two smaller static vents so the power vent would pull from the soffits and not compete with them. (hope that was the right thing to do). Soffits appear to be adequate.
Summary: So I have conditioned my crawl spaces against moisture. I have added attic ventilation. I have had the attic looked at by several people and all say there is proper insulation. But since I just added those vents, there hasn't been enough time to tell if this will solve the problem. I may not know until next year!
I have been running a dehumidifier in the bedroom as it seems the humidity level rises in there (cheap humidity reader from Lowes) . I still do not know why. Addition built too tight and not breathing?
There are a few other things I could try and wonder if others here have even other suggestions:
1) Take the rims off those recessed lights and caulk around them to make sure heat is not seeping in from those. BTW: I don't use these lights very often at all. I have a chandelier in the middle of the room I mostly use along with lamps. The mold is not growing around the recessed lights. Last year I looked these lights up and they were uninsulated lights. So I had someone put insulation on top of most of them (not a fire hazard as I don't use them).
2) Repaint the ceilings with the Zinsers to hopefully seal off any mold spores that remain. This will be one heck of a job! I can not remember if that ceiling was painted with any mold additive or not. It has not been repainted since it was built.
3. Add a ceiling fan to move the air? I currently do not have one in there. I do think there is a temperature differential between the top of the ceiling and the floor.
4. Have someone investigate my HVAC system and duct work? Although had there been any mold I would have hoped they would have told me while doing the work last year when I conditioned the crawl space.
This is driving me nuts as I can't figure it out! Of course those new attic vents were just put in and attic will not be as hot as before. Since I solved the problem in the powder room I can only think the same mechanism is working against me in the bedroom. Hot attic air against colder sheetrock from air-condition causing enough condensation for mold growth. The question would be where is it coming from? Recessed lights? Or do I wait to see if the new power vent has any affect?
Any and all thoughts appreciated!!