Moisture behind installation layer

[Buildgates]

I am expanding my vacation home and have finished insulating the interior. When the space (a bedroom) was heated and used this weekend, I discovered that it was completely wet behind the insulation in the installation layer. The wall consists of a wind barrier, 95 mm insulation, vapor barrier, and then 45 mm in the installation layer. The vapor barrier was wet on the inside.

The question is whether this is normal or if it will cause problems? Should I install an exhaust fan in the ceiling, even though this space is a bedroom?

I suspect the root cause is that the wall insulation is too thin (95 mm) compared to the installation layer. Should I simply remove the insulation in the installation layer to move the dew point outward? Heating costs will be high, but I don’t want mold in the wall.

Grateful for tips and advice!

 

[Gabbe1]

The thickness of the insulation outside and inside the vapor barrier matters. The rule of thumb is that 2/3 should be outside, which you meet. However, in new constructions, materials release moisture during the initial period, which becomes especially apparent when you first start heating. High humidity causes more moisture to condense earlier on cold surfaces.

It may be wise to heat up the room, remove the inner insulation, and run a dehumidifier for a while before (dry) insulation is reinstalled and the walls are closed.

 

[MorpH]

I can start by saying that I have no idea, but creosote usually has a much darker color, dark brown, almost black. Look at a telephone pole, and you can see how they should look. However, these are heavily impregnated, pressure or heat impregnated, so it's possible they've "just" brushed it on, and in that case, it might be much lighter in color. However, there's little reason to treat with creosote on the inside of the attic, so it doesn't seem very likely. I also think it mostly looks like old wood.

 

[Plupp 405730]

I can start by saying that I'm not at all knowledgeable, but creosote typically has a much darker color, dark brown, almost black. Look at a telephone pole and you can see how they should look. However, these are heavily impregnated, pressure or heat-treated, so it's possible they've "just" brushed it on, and if so, it could be much lighter in color. However, there's little reason to treat with creosote inside the attic, so it doesn't seem very likely. I also think it mostly looks like old wood.

Did you reply in the wrong thread? 😉

 

[Buildgates]

The thickness of the insulation outside and inside the vapor barrier matters. The rule of thumb is that 2/3 should be outside, which you fulfill. But it's also the case that in new constructions, materials release moisture during the first period, which becomes particularly evident when you first turn on the heating. High humidity causes more moisture to condense earlier on cold surfaces.

It might be wise to heat up the room, remove the inner insulation and run a dehumidifier for a while before (dry) insulation is reinstalled and the walls are closed.

Thanks for the response. Then I hope this is temporary so I can close up the wall with a clear conscience.

 

[Joak]

Thanks for the reply. Then I hope this is temporary so I can close up the wall with a clear conscience.

What kind of wind barrier do you have? It needs to be a diffusion-open fabric rather than the simpler wind barriers. They are simply too tight.

 

[Buildgates]

The windbreak is T-vind Super. As a vapor retarder, Mataki D20 is installed in the roof and walls.