Should the ETICS (External Thermal Insulation Composite System) be left on or removed on the gable-side extension?

Hello dear ones,
I would like to ask for your advice.
We have a cozy single-family house. We also have one little girl and then came triplets :)
Now the house is too small and we want to build an extension.
The plan is (by now) to extend the gable side by 5 meters.
The house is from 2006 and has an ETICS (14cm insulation).
Our architect asked us whether we want to leave the ETICS on the gable side. We could also immediately lay electrical and heating pipes in the insulation.
The disadvantage is, of course, that the transitions from the old to the new part would then be about 60cm deep.
Also, it somehow feels "botched" to simply leave the old ETICS on.
However, the architect also said that it would be helpful to mitigate any relative building shifts or settlements.
What is your opinion on this?

Best regards
Hendrik

You see me a little confused: I almost would have pointed you to your own thread: - there either you appear twice (probably 1x desktop + 1x smartphone) or a namesake with the same problem (?) - anyway, I advised back then to build a gable-side extension, but then the outer wall would be three-layered ???

The architect also said that it would be helpful to soften possible building shifts relative to each other or settlements.
What is your opinion on that?

Spontaneously: change the architect, how is the ETICS supposed to soften settlements, why should it still be needed on an interior wall, and why does he want to chase slots into it?

Wow, good memory. It seems your nickname is not without reason ;)
In fact, those were our first considerations two years ago. We then went to an architect and experienced a real crash landing. Several thousand euros later, he told us that we should move out for 6 months during the renovation and deviated from his original cost estimate by more than a factor of 2. At that point, we simply lost interest and, like an ostrich, buried our heads in the sand and waited.
Now we want to make a second attempt with a different, this time local architect.

So I take away that we better remove the insulation.
And you would then rather recommend chasing in the new brick interior wall, which adjoins the current exterior wall?

Wow, well remembered.

So you are identical with yourself ;-) and the house is as shown in the linked thread? (that would then have a three-layer outer wall construction – clarify the contradictory information, preferably from the building file).

Now we want to make a second attempt with another, this time local, architect.

My first candidate would be the architect who built the house.

So I take away that we better remove the insulation.
And you would rather recommend chasing in the new masonry inner wall, which adjoins the current outer wall?

The insulation makes no sense on the inner wall. What should be installed where would have to be discussed in more detail. Please get the as-built plans including the site plan with building envelope here into the thread.

Hello,
here is the requested information.

The current exterior wall consists of the brick, insulation, and a plaster coat, and is about 40cm thick. It is not clad or similar.

What exactly you mean by building window is not clear to me. Development plan? (single-story, eaves height 4.5m, site occupancy index/floor space index 0.4; with garage etc. 0.6). I’m happy to provide more on this.

I am unable to upload .pdf files here. If it helps, I can also convert the development plan into images.

For your information:
At "existing building on the plot" I have also marked the 3m boundary.

What exactly you mean by building envelope is not clear to me. Development plan? (single-storey, eaves height 4.5m, site coverage ratio/floor area ratio 0.4; with garage etc. 0.6). I am happy to provide more on this. [...] For your information: For "existing building on property" I have also drawn in the 3m boundary.

Only that these are by no means always – typically even majority not – identical with the area of the property buildable with main buildings called "building envelope."

I am unable to upload .pdf files here. If it helps, I can convert the development plan into images as well.

I can usually work well with both, gladly also by email via gmx (de) behind my member name.

The current exterior wall consists of the stone, insulation, and a plaster coat and is about 40cm thick. It is not brick-faced or similar.

The pictures confuse me: the attachments here are called "measurements," but what use are measurements without dimensions, and furthermore the plans in the old thread (see post #2 here) show with dimensions clearly an approx. 41 cm thick three-shell construction excluding plaster consisting of a 17.5 cm bearing masonry shell, presumably mineral wool or the like and an air layer comprising the intermediate space of 12 cm and a (completely exaggerated as "plaster carrier") 11.5 cm thick facing masonry shell. This remodeling plan does not look like professional architect’s work. Were you the buyer and not the builder / first occupant?