ᐅ Insulate the former conservatory from the outside and from the garage side

Hello,

In our semi-detached house, there used to be a conservatory separated by a typical sliding door. The conservatory was already used as a full living space because it had underfloor heating installed. We have now removed the door and are connecting the room directly to the rest of the house.
The conservatory borders the garage on the left, the street at the front, the house on the right, and has a glass wall facing the garden at the back (see schematic drawing).

I would like to insulate the two walls facing the garage (a concrete wall from the garage side) and the street (an external brick wall). Our energy consultant, who oversaw the renovation according to KfW standards, warned us against doing this carelessly, as it could lead to condensation and thus mold.

Since the energy consultant wants to charge quite a lot for the calculations, I would like to know in advance if anyone here has done something similar and possibly encountered problems?
There is still a lot of polystyrene insulation in the roof that will be removed. Could I possibly reuse it?

Thank you very much in advance

BauBauNRW schrieb:

The conservatory is adjacent to the garage on the left, faces the street at the front, is connected to the house on the right, and has a glass wall at the back facing the garden (see schematic drawing).

I would like to insulate the two walls towards the garage (a concrete wall from the garage side) and towards the street (brick facade on the outside). Our energy consultant, who supported the renovation to KfW-standard, warned us against doing this directly because it could cause condensation and consequently mold.

I have to agree with the energy consultant. I wouldn’t just do it like that; instead, you should look at the whole structure as a unit. What good is it if you insulate only those two walls well while the glass wall may not be properly insulated? In the worst case, that could create a cave-like effect with dripping moisture.