In any case, consult a specialist for advice. Then it can be seen what can be done by oneself. I think installing the insulation oneself should not be a problem.
Oh, thank you very much for your answers. That is probably how we will do it. My husband is looking into a consultation to see what he can do himself, the rest will be done by a professional. I think that is a good compromise.
Yes, I also think it is a good compromise, because this way you can save some costs. I can even arrange it so that the homeowner participates in the insulation measures and has the hours credited, which are then deducted from the total amount.
I once did this with a friend in his old building. It’s no big deal and we carried out the facade insulation. For this, we used mineral wool. The insulation on the sloping roof was then done by a professional.