ᐅ Attic dampness? Condensation?

Created on: 23 Dec 2016 10:45
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Tommes78
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Tommes78
23 Dec 2016 10:45
Hello everyone,
we insulated our attic with thermal insulation and a vapor barrier. The general contractor was supposed to install a cold roof, but since we did the attic conversion ourselves, we insulated it as well. Additionally, the attic is equipped with an insulated loft ladder.
The heating has been running for about 5-6 weeks now and has completed the screed heating program.
Yesterday, while hanging lights in the attic, I noticed water dripping near the chimney and water collected in 2 or 3 spots on the vapor barrier.
I then removed the vapor barrier and the insulation around the chimney. The insulation is completely soaked, but only in that area near the chimney. The vapor barrier underneath, i.e., the one from the roof, is also wet, as are the beams of the roof structure.

My site manager says it is condensation, but I find it strange that it occurs only near the chimney. He said the chimney is close to the loft ladder, which is not fully sealed yet, and that’s why condensation is forming there. He suggested sealing the ladder tight, which I have done, but I still find it hard to believe it is just condensation since the attic hasn’t actually been cold. What do you think?
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Knallkörper
23 Dec 2016 10:55
The humid air might have entered the attic through the staircase opening, then passed through the vapor retarder, and condensed on the cold breathable roofing membrane. Perhaps the vapor retarder is poorly connected at the chimney.

What I wonder is: Do you really have a vapor retarder there, or is it a vapor barrier??? Is there insulation between the attic and the upper floor as well?
tomtom7923 Dec 2016 11:04
Well, a cold roof—who calculated this for you? Where is the dew point now, and how warm is it currently on the roof?
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Tommes78
23 Dec 2016 11:13
Between the attic and the upper floor, there is insulation, and the attic itself is additionally insulated. There is a vapor retarder.

What I noticed was that the membrane had come loose on one side of the house wall and was therefore not properly sealed, but that does not explain to me why it is damp specifically around the chimney.
tomtom7923 Dec 2016 11:22
Maybe the chimney is cold? How is it insulated? Previously, the roof was cold, now it is warm, so condensation occurs.
K
Knallkörper
23 Dec 2016 11:24
The chimney could be the coldest spot. The chimney essentially acts as a thermal bridge. Maybe you haven’t found the other damp areas yet. However, the overall workmanship is more than questionable. Do you know the Sd values of your vapor retarder and roofing membrane?