ᐅ Electrical installation beneath an external thermal insulation composite system (ETICS)

Hello everyone,
I have another question regarding the electrical installation.

I want to route the electrical wiring for the upper floor on the exterior facade to the technical room in the basement.
The facade will be insulated with 10cm (4 inches) of mineral wool boards.

My idea is to use a cable duct about 4–6cm (1.5–2.5 inches) deep and approximately 16–21cm (6–8 inches) wide, which would later be covered by the insulation.
On both the upper and lower floors, one hole each would be needed to route the cables outside.

Is there anything I should consider here?
For example, how many centimeters should the insulation cover the duct at a minimum to prevent issues like cracking?
Is a standard cable duct sufficient, or are there specific fire protection requirements since it would be installed directly beneath the insulation?

Regards,
Chris

Can’t you discreetly install a small distribution box somewhere for the upper floor? A cable duct measuring 21cm by 6cm (8 inches by 2.5 inches) is quite large.

Hi, the upper floor will have its own sub-distribution board. Electrically, only one 10mm² (10 AWG) cable is planned to supply the sub-distribution board. Additional cables will include coaxial (about 5) and network cables (about 14).
It might also be sufficient to use a slightly smaller cable duct, for example, 160mm (6.3 inches) wide...
But it's better to allow some extra space than to run out of room in the end!

My question is more about the basics,
meaning cable duct overlap, fire protection, and so on...

If your facade is insulated only with the 10 cm mineral wool, 4 cm of additional insulation would be clearly insufficient for me. I seem to remember you mentioned timber frame construction elsewhere, so there is probably cavity insulation as well – in that case, the situation is somewhat more relaxed.

I would still consider two options in your situation:

Either put everything into one installation shaft (which can, for example, be built as a projection on the facade and properly over-insulated) – this way you might have the opportunity later to use it for other purposes, like pulling additional cables.

Or significantly reduce the number of cables (e.g., a switch upstairs with an uplink going down; there are also various approaches for coax), and use a certified system for outdoor installation, such as Fränkische FFKu-ReMo. Depending on the case, it might be possible with a maximum of 3 to 4 conduits. This gives you a solution that the manufacturer has tested and approved for such purposes.

You are certainly aware that network and coaxial cables should not be run “just like that” together with power cables – at least separation partitions must be present inside the conduit. However, for high-load cables (such as floor distributor connections), I would never consider running them together with network/coax cables.

Harakiri schrieb:

If your facade only has 10 cm (4 inches) of mineral wool insulation, 4 cm (1.5 inches) of additional insulation would be clearly too little for me. As far as I recall, you mentioned timber frame construction elsewhere, so there is probably cavity insulation as well – then everything is somewhat more relaxed.

The timber frame part is on the other side of the building... 😉 Here, an additional storey was built using timber frame construction.
The existing building is masonry – 30 cm (12 inches) thick walls – and will be insulated during this process (10 cm (4 inches)).
So my idea would be to remove the exterior render as much as possible (it’s a very rough render), attach a cable duct, and then apply the thermal insulation on top of that.

Harakiri schrieb:

I would still consider two options if I were you:

Either put everything into one installation shaft (which can, for example, be built out as a projection on the facade and properly overinsulated) – then you might have the chance later to use it for other purposes, like pulling cables again, etc.

I had thought of something like that as well. It just seemed much more complex compared to the cable duct option.

Harakiri schrieb:

Or significantly reduce the number of lines (e.g., switch upstairs with uplink going down; for coaxial cables there are also various approaches), and use a certified system for outdoor installation, such as Fränkische FFKu-ReMo. Depending on the situation, maybe max 3 to 4 conduits would suffice. This would give you something that the manufacturer has tested and approved for these purposes.

Do you mean using multiple empty conduits with cables separated instead of one large cable duct?
I plan to have a network cabinet in the basement. From there, I want to connect all outlets, including TV cabling. I know it’s possible to daisy-chain outlets (which is already in place today). However, my plan was to run everything in a star topology from the equipment room.

Harakiri schrieb:

You surely know that network and coax cables should not be laid "just like that" together with power lines – there must be at least partitions in the cable duct. But in my experience, with heavily loaded cables (such as the connection to floor distributors), I would never consider laying them together with network/coax cables.

I am aware of that. My electrician said it wouldn’t be a problem with the intended lengths we’re talking about – possibly around 4 meters (13 feet).
But as mentioned before, it might be an option to separate power and coax/network into different empty conduits.
That way, the overall build-up won’t be as thick!

OK, if it’s masonry, why make it so complicated? You, or better yet an electrician, can chisel out the cable routes and install everything neatly inside, then plaster over it, and just as easily insulate without any weak points, and so on.

It would still be advisable not to combine everything in one place, but rather to plan the chases as small as possible and with proper spacing, ideally in consultation with a structural engineer.