What is wrong with the construction? Moisture in exterior walls

[calle3487]

Hi,

I have some exterior walls that have been additionally insulated from the inside as follows:

From inside to outside:
Gypsum
Construction plastic
145mm glass wool
Half brick
Air gap about 3cm (not ventilated with outside air)
Full brick

I have found during hole drilling in the interior wall that the RH is too high (around 70-85%), which of course is not good, no visible mold, but it seems to be just a matter of time with these levels. I also understand that interior insulation is not optimal but don't really understand why it doesn't work technically when there is actually an air gap that should prevent driving rain from entering the structure and plastic inside that should prevent moisture in the room from entering the wall.

Could it be the absence of head joints in the outermost brick wall that is the problem, i.e. moisture from driving rain penetrates the façade and is not ventilated out and instead finds its way into the structure? Is there any risk with creating openings in the joints from the outside to create a ventilated air gap?

Can someone enlighten me with some knowledge and preferably some form of reasoning on why this obviously doesn't work?

 

[Tomture61]

Googled brick wall, the first thing that comes up Bricks easily absorb moisture because they have a significantly more diffusion-open surface than other building materials Additionally, the facade is unventilated and you have plastic in the wall.

 

[calle3487]

I want to clarify that the humidity level of 70-85% is within the inner wall layer. That is, between the original back wall and the fiberglass insulation "in the house." Is there any way to address this, or does it involve tearing down to the original construction and living with the fact that it will be freezing cold indoors in the winter?

Or could the ventilation of the channel between the brick layers solve the problem of high humidity in the inner construction, you think?

I have done a few measurements that suggest the humidity in the air gap between the brick rows is roughly the same, 70-85%. Much higher humidity compared to outdoors at least. Hence the idea of ventilation.

Regards

 

[calle3487]

Googled brick wall, the first thing that comes up Brick easily absorbs moisture because it has a much more diffusion-open surface than other building materials
Additionally, the facade is unventilated, and you have plastic in the wall.

Thank you for your comment.

I have read so much about this but feel that about half claim that plastic is a must and half claim that you absolutely should not use plastic. My perception is that a vapor retarder would have been more suitable, but I can't see how this construction really differs much from a modern construction with a brick facade aside from the ventilation of the air gap. And in modern constructions, I believe most agree that plastic on the warm side is what's "right." This house is at least 100 years old.

 

[Tomture61]

Thank you for your comment.

I have read a lot about this, but it seems like about half say that plastic is a must and half say you absolutely shouldn't use plastic. My impression is probably that a vapor barrier would have been more suitable, but I can't see how this construction really differs much from a modern construction with a brick façade apart from the ventilation of the air gap. And in modern constructions, I think most agree that plastic on the warm side is what's "right." This house is at least 100 years old.

Using a vapor barrier (plastic) in a stone house that is 100 years old + additionally insulated on the inside with mineral wool is completely the wrong way to carry out energy-saving measures. A barrier does not belong in a climate shell with that house; the insulation should also be on the outside of the house for best comfort and to utilize the mass in the brick wall.