improper sealing of duct through roof?


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Old 05-04-22, 04:35 PM
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improper sealing of duct through roof?

A recent inspection showed a good deal of mold in the attic. Mold remediation company says they see daylight around the bath fan exhaust duct going out the roof. I have a poor quality photo showing this. They suggest improper sealing around this duct can cause moisture to get in and lead to mold. We had a leaky roof so got a new one put on about 16 months ago. Perhaps something happened when roofers replaced the vent hood that was covering this (a typical Braun bath fan vent hood)?


My questions are:
1. From what little you can see in the photo, does it seem like improper sealing of the vent hood or are there other explanations for the daylight?
2. If moisture is getting in there, could it be enough to cause a good amount of mold in 16 months?
3. If not enough to cause excessive mold, what are other potential causes? We did have roof leaks, and apparently a soffit panel at the eave is loose.
Thanks
 
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Old 05-04-22, 05:10 PM
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Can't tell you much without seeing the outside louver on the roof. The roof vent should not leak no matter if the vent duct is hooked up or not. So IMO it's possible the light is not necessarily an issue but it depends on the exact kind of vent that they used.

If the mold is only around the vent then sure, the vent could be responsible. If it's everywhere that is likely from generally having high humidity in the entire attic, poor air sealing (of penetrations in the house ceiling & top plate) and possibly poor attic ventilation. Living where you have cold winters and an inadequate amount of insulation can cause it too. Hopefully your clothes dryer does not vent into the attic.

My guess is you are seeing years worth of mold buildup.
 
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Old 05-04-22, 08:48 PM
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Thank you. The mold is concentrated in the general area of the vent and not throughout the entire attic. Clothes dryer does not vent into the attic, and there is blown in insulation there but who knows if it is adequate. The house is in the mid Atlantic so not extremely cold winters.

The roofer has agreed to take a look at the vent but I wanted to have some more information from unbiased sources. Appreciate you chiming in.
 
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Old 05-04-22, 08:51 PM
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If the area is directly above a bathroom with a shower you're going to have more humidity above that area than normal, due to hit steamy showers,
 
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Old 05-05-22, 04:11 AM
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Really hard to tell from the picture but it looks like the mold extends a little below the vent but is mostly above the vent.

If this is true then I doubt that water is getting in from outside at the vent as water does not run uphill.
So if I am correct there is either a leak higher up or the vent hose/pipe is leaking at the vent cap
(probably the vent is blocked also)
My theory here is that moist warm air does rise and if it escapes it will condense on the roof
 
 

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