Foam glass gravel yes/no?

There are no vapor barriers in practice for such things at all... only brakes, if you mean foils.

And under tiles, for example, this is not done at all.

A seal against rising moisture is usually always done with bitumen sheets, and it is not difficult to apply. Or did you mean that as a barrier?

From this perspective, I still don’t see a problem here where you want to see one.

By the way, the installation of perimeter insulation under the slab is not as simple as on the walls. Additionally, there is the extra effort regarding the ring earth...

a vaporbarrier above the insulation is necessary to keep the indoor air humidity away from the surface of the floor slab.

In the picture you posted it explicitly says "vapor barrier." Although personally, as a layman, I don't believe that indoor air diffuses through the finished floor and the screed. Be that as it may, I consider the "foil" on the "tacker plate," on which the underfloor heating pipes lie, to be sensible, if only to prevent the wet screed from saturating the underlying insulation. Once the screed is dry, I see no more problems. Experts may correct this...

Then there is the scenario of a leaking heating pipe, but in that case, you probably have to tear everything up anyway, so the insulation hardly matters.


In practice, of course, on the one hand, foil is laid and taped, but on the other hand, at each of these blue rings, there is again a hole in the foil. Well, practice/theory. It’s fine.

To cut a long story short, I will simply draw a conclusion now: there are different pros and cons as well as various challenges in professional execution for both internal and external insulation. My favorite is external insulation (that’s how we will do it), and builders who have done it differently find their solution better and also have enough arguments for it. My arguments in favor of external insulation: - thermal bridge-free construction without extra effort - more available room height in the basement with the same shell height and same insulation thickness - fewer building physics problems I cannot judge whether the whole thing is more expensive in the end under the same conditions than internal insulation, but I think the difference is not that big.

So it is a basement after all - then your U-value calculation is incorrect anyway, because such ground temperatures do not exist

And no extra effort? Sorry, build first, then you will know that it actually is extra effort and therefore more expensive. Just the ring earth electrode alone, which is often not done - but is a must.

And you simply claim it is easier in terms of building physics - precisely because you are so convinced of your position.

I do not want to dispute the advantages (less thermal bridge, more construction height (although we are talking about a few centimeters)), but please stick to the facts.

But you do not want to hear anything else anyway, otherwise you would not display such a "my way or the highway" mentality.

But you don’t want to hear anything else anyway, otherwise you wouldn’t show such a bossy attitude.

I get a lot accused of me, but definitely not that! I just had the impression that I could write whatever I want and you would twist my words in the following post again and again so that you confirm your opinion (q.e.d. ). Besides, I didn’t contradict anyone or speak badly about anything, so portraying me as resistant to advice is not fair.

One can certainly have different opinions about the topic of building physics, but I think it can generally be said that exterior insulation is better under that aspect than interior insulation. Every insulation layer that has contact with interior surfaces must be protected against penetrating moisture by a vapor barrier or the like – in my opinion, this applies not only to walls and ceilings but also to the floor. With exterior insulation, this is not necessary because the problem the vapor barrier is supposed to protect against simply cannot arise.
Regarding the mentioned effort for grounding, it is mainly about the financial cost, which according to offers we have is about twice as high (approx. €300). How much extra work that is I don’t know, but I don’t have to do it either.
The additional effort for the same interior height is significantly greater because the 14 cm we put under the floor slab would mean that all basement walls and the corresponding insulation would have to be larger. The same naturally applies if you build without a basement.

From your point of view, where are the advantages of interior insulation?

Oops, double.

But you are definitely right: you lose a few cm - but don't overestimate that. We have a total buildup of 14cm in the basement - that is not excessively much. The screed needs 6-7cm and despite insulation under the floor slab, you still need insulation below (if high quality). Then something might still need to be installed there - in our case drain pipes and some electrical.

Well, and then you already have your 14cm and then the external insulation won't help you anymore in terms of more height.