ᐅ Issues with Moisture in Older Homes

Hello everyone,

I have a problem with humidity in my apartment.

All rooms have humidity levels between 55% and 70% despite regular ventilation.

A few months ago, we had mold remediation done, and now we want to solve this problem because we only took ownership of this condominium a few months ago. The previous owner paid for the mold remediation.

Each room has a 100mm (4 inch) hole for air exchange.
There is a fan in the bathroom that is supposed to create negative pressure inside the apartment.
I think this system simply does not work properly.

Now, my idea is to install a decentralized ventilation unit in each of the 100mm (4 inch) ducts, set to activate based on certain humidity levels, and then I would have peace of mind.

However, I am not sure if the 100mm (4 inch) duct diameter is sufficient.
Increasing the size is difficult because I need approval from the other owners, and that takes time...

Would this work?

Thanks in advance for your opinions.

bluetoothtony schrieb:

The mold remediation was still paid for by the previous owner.

That’s where the story seems to begin: What exactly happened there? What was remediated and why?

bluetoothtony schrieb:

We have a 100mm (4 inch) hole in every room for air exchange.

A hole in the wall to the outside??? Like looking outside and hoping no animals get in and that there won’t be drafts?

In summer, you bring in all the humidity through it, and in winter, the walls cool down as if there is no tomorrow. Then the walls get so cold that the moisture in the air condenses there (Google “dew point”), and mold starts to grow.

The idea of a decentralized ventilation system is good, and 100mm (4 inch) pipes (or 105mm) are sufficient for that. Usually, you need a slight slope on the borehole so that condensate can drain outside. Get a company that knows what they are doing to implement this for you...

bluetoothtony schrieb:

All rooms have humidity levels between 55 and 70% despite regular ventilation.

So? Those are normal values. You have exactly the same levels now with a decentralized ventilation system.

Currently, I have 92% relative humidity at only 12°C (54°F) outside, which corresponds to about 52% relative humidity at 21°C (70°F) indoors. You won’t be able to change that by any means (except using dedicated dehumidifiers).

Other than that, I can only agree with the previous speakers. A ventilation system with heat recovery provides hassle-free air circulation—but it can’t work miracles.

ypg schrieb:

You can already get a hint of the beginning: What happened there? What was renovated and why?

We had mold on two exterior walls.
A mold specialist inspected all the rooms and concluded that the mold was likely caused by cold exterior walls and poor air circulation (the bed and couch were placed against the walls).

The entire plaster was removed, and then calcium silicate boards were installed.

SoL schrieb:

A hole in the wall leading outside??? Like, just looking out and hoping no critters get in and that there’s no draft?

We have a 100mm (4 inch) hole in every room with a plastic flap covering it.
Inside, there is only a mesh screen to keep insects from entering the apartment.

But no fans or anything like that.