Remove old fiberglass insulation?

Hey, The black spots arise in my opinion due to convection currents. The material takes on a sort of filter function and discolors. I believe mold forms in rare cases, except if the glass wool is in water. As long as this glass wool is installed, it insulates.

For your construction project, it is advisable to plan the work. Of course, experts should be involved.

Best regards

First of all, thank you very much for your answers. I have now decided to renovate only what is visually important. I will leave the rest alone for now.

However, having such a sample taken also costs some francs. I don’t know the exact amount now, but it’s definitely not free.

I also discovered that the [Unterspannbahn] has several holes. Otherwise, everything there is fine. Some time ago, I had the roof cleaned with a high-pressure cleaner. During this, some tiles were pushed back by the water. But they stayed behind the foil. I asked the roofer to take a look at it and he advised me to install a second [Unterspannbahn] from the inside. I think I will do that.

I just thought of something else and I have another question about improving the insulation. In my opinion, this energy saving doesn’t really help much.

Does it make sense if I fill it with sealant? Or should I rather leave it be?
Thank you very much for your advice.

Hello,
An inventory is required here. The information about the exact roof structure with layer thicknesses must be provided.

The discoloration is 99% likely to be a contamination and not mold. Usually, old mineral wool always looks like this.

I suspect that your rafters are not fully insulated either. If you now apply full rafter insulation, you won’t be the first to soon be able to dispose of your roof structure as compost.

A specialist is needed here and only they can assess this.

Best regards