How to close the hole for the wall box?

Hello everyone,

a breakthrough was made through the double-shell masonry for our container fan.

Questions:

how should I best close the hole, both from the outside and from the inside?

I am thinking of the following:

- Foam? If yes, is there a special one?
- Styrofoam?
- Mortar?
- Plaster?

I also read somewhere that you should use a compression tape for the wall box, it gets a bit tight there.

The screed is already in.

Can only contribute to a limited extent. I will install the wall box over the weekend. It will be foamed with construction foam, the rest will be done by the plasterer.

But I have a quick question. Did you lay the flat duct directly on the raw floor or did you put something underneath/insulate it?

I have a quick question. Did you lay the duct directly on the raw floor or did you put something underneath/insulate it?

The duct was placed on the welding membrane, with a thin layer of foam in between so the plinth fan should fit better.

The duct was laid on the welding membrane, with a thin layer of foam in between, so the plinth fan should fit better.

Thank you, but I didn't quite understand or we talked past each other. I wasn't referring to the wall box but rather the installation of the duct up to the "point of use." In one picture, it looks as if you laid it directly on the floor without anything underneath. My kitchen fitter mentioned insulation, and the architect said yes, you can put something underneath. When I asked what, answers ranged from thin styrofoam to some kind of fleece. I've also often heard that it's not necessary. Now I'm a bit puzzled about what to do.