Bathroom ceiling moisture + inadequate insulation

Completely airtight is ALWAYS bad. Nowadays, it is rarely done. Better use a vapor retarder! With a vapor barrier, every small mistake catches up with you immediately.

Otherwise, don't forget the vapor pressure. You can Google it. Even a controlled residential ventilation system doesn't help against that at all. It only optimizes the acute moisture balance.

This is not a cold roof, but a warm roof that is not properly sealed and insulated. That’s why everything condenses on the membrane. I would therefore seriously consider the tip about ventilating, especially without controlled residential ventilation. That means even if it’s -10 degrees, you should shock ventilate the place several times a day, otherwise you won’t be able to live there mold-free for long.

Wouldn’t it be more correct, still under warranty, to consult an expert to check whether the roof with insulation and sealing was properly executed? (I mean: No) If not, a comprehensive dismantling of the drywall elements is due. Water and wood will not become friends just because they are close to each other in this house :cool:

completely airtight is ALWAYS bad. Nowadays, people do it only rarely. Better use a vapor retarder! With a vapor barrier, every little mistake will catch up with you immediately.

Otherwise, don't forget the vapor pressure. You can google it. Even a controlled residential ventilation system doesn't help against that at all. It only optimizes the acute moisture balancing.

early versions were called "intelligent foil". Lets in as much moisture as it lets out. Vapor regulating, basically ...

Hello everyone,
I checked at my place... so the vent pipe is completely insulated with us.
Out of curiosity, I removed an LED spot right after I bathed the kids and inspected the ceiling. Everything is dry, but we also have a controlled residential ventilation system from Nilan ( ( Compact p Air 9)) . From my own experience, I can recommend this to every builder. My construction manager is an expert... he is visiting me tomorrow, I will show him the pictures... I will get back to you...

So far, we are managing very well without controlled residential ventilation, also without excessive airing. We have a provision for ventilation, i.e., a small core drill hole in the ceiling to the attic. A plastic pipe is already installed there. When it was still not insulated last winter, it was very easy to see how the rising moisture condensed toward the cold attic. I hope to be able to install ventilation soon, or have it installed. Preferably professionally.

My site manager is an expert ... he is visiting me tomorrow, I will show him the pictures... I'll get back to you...

Thank you

and also thanks to everyone else.

We actually never had problems with ventilation before. Of course, in a new building there is always some residual moisture at the beginning, but we really ventilate sufficiently.