Work on basement ceiling insulation with stone wool

Your answer was the same as mine... Yes, because of the basement bar and large room, many birthdays, parties, etc. So far I have removed 2 panels. Unfortunately, no 60mm panels planned there. But the message is understood. Leaving 60mm out completely would of course be better.

@everyone
I still have to say something about moisture...
I had insulation between the rafters made of rock wool. At the time it was done without a foil on the outside. So directly visible under the tiles. 10 years later the insulation had shrunk so much that the outside air could pass directly through the gaps between the rafters. I think this had to do with moisture. That’s what I wanted to prevent in the basement. After all, rock wool absorbs more moisture than a polystyrene board. Maybe it will smell musty in the basement if the wool has absorbed moisture? Should the gaps between the boards and edges be sealed, filled with putty? Should the edges be filled with foam?

Are there special plugs and adhesives for the insulation boards? Has anyone had good experiences with a manufacturer and type?

Look for insulation anchors or insulation hammer plugs and take the smallest ones you can find. Probably 8mm / 80 mm or so. For adhesive, look for adhesive mortar or use tile adhesive; "flex" is probably not necessary for the described application.

I had a between-rafter insulation made of stone wool. At that time, it was done without foil on the outside. So directly visible under the tiles

Between-rafter insulation in the roof is not the same as basement ceiling insulation under a concrete slab. In general, the same applies to the basement ceiling: glue tightly edge to edge without air gaps and fill gaps. In the case of stone wool, not with foam, but with leftover pieces or mineral stuffing wool. Vapor barrier, foil, or anything else is not necessary: there is no wind and no birds above the concrete ceiling and in the basement (if there are: rebuild the basement walls).

Halving should generally be possible; they can also be cut crosswise and glued together.
The prepared surface will then be lost, so I would additionally dowel it to ensure stability.
What is the construction year of the house, or do you have information about the existing screed?
For anything from 1978 onwards, I wouldn’t worry about an additional 3 cm insulation from below.
For older buildings with only 0-2 cm insulation thickness (of which only a little remains after 40+ years), that can help, but of course 6 cm is better.

You would like a bit of explanation. So basically, insulation for a house built from 1978 onwards doesn't make much sense or isn’t really worthwhile.
And can you, based on your experience, say which insulating material and thickness are sufficient (considering price-performance ratio)?

Thank you very much

Would you like to elaborate a bit? So insulation of a house from 1978 onwards doesn't really make much sense, or isn't really worth it. And can you say from your experience which insulation material and thickness are sufficient (price-performance wise) ;)

thank you very much

From November 1977, the first Thermal Insulation Ordinance applied, which prescribed a minimum thermal protection for components. Since then, at least 6 cm of thermal insulation has been installed in the area of the floor slab. I wouldn't worry about more than 3 cm extra - the first centimeters are the most important. If there is room for 10 cm (and the insulation material is as inexpensive as in 2021) you can add more there. Price-performance wise, the cheapest is 10 cm mineral wool - if there is space. Otherwise, 6 cm PUR, which has a comparable effect but is more expensive, yet thinner. For underfloor heating, 10 cm PUR or 14 cm mineral wool.

From November 1977, the first thermal insulation regulation applied, which prescribed a minimum thermal protection for components. In the area of the floor slab, at least 6 cm of thermal insulation has been installed since then. I wouldn't worry about more than 3 cm extra - the first centimeters are the most important. If there is space for 10 cm (and the insulation material is as cheap as in 2021) you can add some more. The most cost-effective option is 10 cm of stone wool - if there is space. Otherwise 6 cm PUR, which has a comparable effect but is more expensive, though thinner. For underfloor heating 10 cm PUR or 14 cm stone wool.

Yes, there is underfloor heating. But an additional 14 cm of insulation is quite a lot (I still want to use the basement partially) :) You say 10 cm of stone wool doesn't bring much?