Comparison of internal and external insulation: Is external insulation significantly better?

Thank you very much for the answers. The suggestion from is great. I was also planning to start on an old shed wall with sandblasting and re-pointing (there only for aesthetic reasons, no heating or insulation intentions). Then the energy-saving inspector can immediately see what I have done wrong on the exterior wall, and the work on the old residential building would be the second attempt, so "for a friend". And also thanks for the hint about sealing.

Thank you very much for the answers. The suggestion from @11ant is great. I intended to start on an old shed wall with sandblasting and regrouting

That was from in post #17 ...

And also thanks for the hint about sealing.

... and you mentioned that yourself in post #15 :-)

you don’t want to feather your own nest with someone else’s feathers? But it still belongs to you, because I meant your suggestion to request the "Energiesparkommissar" for an assessment in SU. :)

to request the "energy-saving commissioner" for an assessment in SU.

You misunderstood me: SU is clearly more than 50 km away from DA, and such radius indications are usually meant literally by competent professionals. However, I think you should get advice from him when setting up your internal insulation and also travel once to DA for that. I see that further matters can then be handled via video conference or similar. But I suspect an on-site appointment would not be economical for him (I myself have also served clients with long distances – but that only works at expense reimbursement, which fewer than one per year is willing to pay; hence probably his radius indication).

You can also check if the IG Bauernhaus has contact persons in your region. They can often recommend skilled craftsmen and energy consultants.