So I did this inspection for a nice you g couple about 3 months ago. Just last week the girl emails me saying she’s seeing moisture stains on her ceiling right next to the attic access. She’s not mad or thinks I missed something but we always help our clients out when something happens regardless. Anyways so I get there and the osb holding the insulation back is wet and alittle moldy on the insulation side of the attic. The weather stripping is good and the RH is alittle high (just above 50) the humidifier was at 40 RH. Anyways I’m thinking that the moisture is getting into the attic via a gap through the trim instead inside of the actual access. Cause somehow it is getting through to the attic.
Anyways I’d appreciate your guys opinions on what might be going on here. The attic itself is very well ventilated so it’s definitely from moisture coming up from the house.
So where is the OSB? Around the opening? Is it vertical or laying flat?
If you insulate the attic floor, it is also important to have a vapor barrier in place , to prevent warm, moist air from rising into the chilled attic from the living space below. The moisture will condense on the wood and insulation, reducing the insulation R-value and encouraging the growth of mold and mildew.
Scott, That is correct advice for where you live and for any climate with more than 8000 Heating degree days but for most climates in the USA you would actually want a vapor retarder, not a vapor barrier. I don’t know the location of the OP
Did you exclude roof or vent leaks, drips from above to the area?
I agree the location near the poorly sealed attic hatch is suspicious for a moisture/condensation/vapor issue.
In the 3rd picture down, on the right, is that duct work?
If it is, there can’t be much insulation under it and warm air could be passing into the attic from under that and condensing on the cold attic side top of the drywall and spreading from there.
Just a thought…
Need more/better pictures of the attic area in question here.
What is on the other side where the mould is visible?
To help a better understanding of the house is needed. Age of construction to understand building practice as well as old houses with new windows and HVAC equipment can cause issues as it changes the way the house operates , amount of occupants? the HRV is set to recycle air not exhaust and recycle. Is this the primary exhaust? Is the HRV balanced and operating properly? Is the HRV original to the house or add on to attempt to control humidity? That is a big difference between HRV reading of 37 and 50RH. In Edmonton 50% is high now with our temperature dropping. Are the homeowners using additional portable humidifiers? Thermal imaging and depressurization would assist. If it is at the attic hatch there is a good chance leakage is at other penetrations of attic. Homeowner education may be required. Attic ventilation can actually increase moisture issues.
Lots of information is required to diagnose these issues.
Here we go again. Let’s bounce that ball back and forth.
Because it is localized at the attic entry point. I think this is good ol stack effect causing vapor movement across small openings which then condensates.
Oya definitely has a vapor barrier, just on the other side of the barrier holding the insulation. Like it right on the otherwise of the osb. Go up into the attic and there’s your barrier right there. It’s on the other side
No sorry for the bad pictures they are all I have for now. It’s the other side of the barrier that holds the insulation and prevents it from falling through the hatch.
For more context this mold is on the other side of the dam. The vapor barrier is very much there and the ventilation is pretty good no signs of any other moisture in any other part of the attic. So it’s very likely moisture is escaping through the home and condensing on the cold surface of the dam. The only issue is that they have good weather stripping. Meaning the moisture is coming from somewhere else. I’m thinking there is a gap between the hatch and the ceiling right where the trim is and the gap is not sealed. Allowing moisture to enter the attic and get the other side of the dam
Steven, you don’t have to know for sure. But, refer it out to an insulation contractor to assess and remedy the moisture issue that will cause more damage if not fixed.
Using @sbridges2 cool illustration, I agree and I would caulk here and see what happens (after replacing damaged materials)