Internal insulation or wall construction problematic?

Good morning,

I hope I have arrived in the right subforum. Unfortunately, I found nothing relevant through the search.

It concerns the purchase of an existing property. Overall, it would be very suitable for us, but the crucial question arises regarding the wall construction. Briefly the framework data: It is an end-terrace house with 2 floors and a converted rafter roof and basement. Living area about 150 sqm. Year of construction is 1979. Since we are complete laymen, we had an inspection with an expert. Unfortunately, we are now faced with great uncertainty regarding the wall construction, which unfortunately could not really be dispelled or clarified by the expert either. There is no possibility of getting an enlightening view of the cross-section or similar. According to the construction description, the wall construction is as follows: 11.5 cm facing bricks (calcium silicate bricks) and 17.5 cm Leca backing wall, 4 cm rigid foam, 1 cm plasterboard. I have read that interior wall insulation is almost always problematic. For us, the question now arises whether we really have to expect fungus growth behind the plasterboard or whether such constructions are, according to experience, perhaps unproblematic after all. And if not, what measures should be taken?

Thank you in advance.

Rigid foam acts, as far as I know, like a vapor barrier/retarder. So, if it is installed properly, little moisture will reach towards the exterior wall. What is actually always interesting is whether enough warm air along with humidity can reach towards the exterior wall and condense there. Then it also depends on whether the condensed water can evaporate or not. Maybe go again with another expert. If the property is interesting, the money should not be a bad investment, and if bad news come, just don’t buy. Basically, you can’t lose. Interior insulation doesn’t have to be a bad thing either.