Condensation in outer corner

[Harey]

Hello,
I was building and was about to finish OSB-Gypsum when I discovered condensation.

I checked the entire house; it seems that there is condensation in all the exterior corners of the house.

Is it poorly taped between the plastic ceiling-wall?

I followed the instructions, at least 20cm overlap, taped wall plastic to ceiling plastic, then clamped with a 45x45 installation layer batten.
When I feel with my nails, the tape hasn't come off or bubbled anywhere; it is tight.

I have underfloor heating on and no direct ventilation, just slightly opened the facade vents. No dehumidifier either. The house was sealed in July/August.

Can anyone offer tips and help?

 

[Centano]

On which side of the plastic is the condensation, towards the room or on the side facing the insulation?

 

[Harey]

On the inside of the plastic, i.e. towards the room against the gypsum.

 

[bossespecial]

Is there heat indoors?

 

[Harey]

Yes,
Between 15-17 °C indoors...

 

[Anonymiserad 405730]

Yes,
Between 15-17 °C inside...

Constant?

 

[Anonymiserad 405730]

On the inside of the plastic, i.e. facing the room against the gypsum.

It could be construction moisture that cannot dry out as the ventilation is not operational during the construction period…
Is it a concrete slab?

 

[Harey]

Constant?

Yes, constant.

 

[Harey]

It could be construction moisture that cannot dry out because the ventilation is not running during the construction period…
Is it a concrete slab?

I thought about that too... maybe using a dehumidifier could work?
Yes, slab on ground 300mm insulation underneath and underfloor heating.

 

[Anonymiserad 405730]

I thought about that too... maybe a dehumidifier would work?
Yes, flat on the ground 300mm insulation underneath and underfloor heating.

Dehumidifier works fine. Would have left open in a problematic corner until you see that the problem is gone.

 

[Harey]

Dehumidifiers work fine. I would leave it open in a problematic corner until you see that the problem is gone.

What do you mean by leave it open?

 

[Anonymiserad 405730]

What do you mean by leave open?

Not plastering it up again so that you can see if the moisture disappears through the dehumidifier, if you choose to do that…

 

[Patzie]

It could also be if the insulation has been neglected in the corners, then the plastic becomes ice cold there and warm air condenses against the cold plastic. (Think cold beer from the freezer in the summer)

 

[Harey]

Could also be if there has been carelessness with the insulation in the corners, then the plastic becomes ice cold there and warm air condenses against the cold plastic. (Think cold beer from the freezer in summer)

I had that thought too but wouldn't the condensation then occur along the entire beam/timber since it goes all the way from the air gap outside to the plastic inside?... or am I thinking completely wrong?

 

[Karl-Ove Qvarfordt]

In all corners (inside view), a geometric thermal bridge occurs, therefore you get condensation first in the corners. Run a dehumidifier.