Foam glass gravel yes/no?

14cm Styrodur under the floor slab
Floor slab
Knauf Katja Sprint
3cm EPS 035 DEO multipurpose insulation board
3cm EPS 035 DES impact sound insulation board
6cm screed with underfloor heating
1.5-2cm floor covering

> Floor structure inside approx. 14cm
> U-value 0.18 W/m²K

Our wastewater pipes run vertically through the floor slab and are redirected below or run in pre-wall elements. We do not need any space for this.

Impact sound insulation in the basement? Good planner... also penetrations of the floor slab - we have deliberately avoided that. So, now you have the same construction height as me (I have 7cm insulation...) - where is your gain now? Oh yes, the U-value is 0.06 better

We will achieve Kfw55 and that was the goal. If I leave out the 14cm under the slab, I get a U-value of 0.49 W/m²K or, with 7cm insulation, 0.43 W/m²K. You might want to recalculate your 0.06.

Impact sound insulation is not only there to reduce impact noise downwards (greetings to the moles), but also for structure-borne sound insulation. In addition, the panels (Rolljet) accommodate the pipes of the underfloor heating.

What is to be objected to penetrations of the slab if they are professionally sealed? In our case, through pipe collars that are cast into the slab.

Since you are all-knowing, you surely know what I insulated with (which I had already mentioned here)

PUR...

And structure-borne sound definitely not - floating screed. By the way, I can't hear any difference from above here - it's just obviously "very hard" to walk on.

If properly sealed, it's of course no problem - but it is one more potential point of failure. And in case of need, you practically can't get to it anymore.

I simply take the information that is directly available and there was no PUR mentioned. But you could also mention the thermal conductivity group, then I would have to speculate less.

The best one I quickly found offers WLG 021 and thus at 70mm a U-value of 0.3 W/m²K. However, per square meter it also costs more than our 140mm XPS boards.

Isn't it rather unorthodox not to lead the wastewater pipes directly outside?

By the way, we are slowly but surely drifting completely away from the actual topic. I have presented my arguments as to why I would prefer exterior insulation. No one has yet convincingly explained why interior insulation should be better. Only that it is cheaper (which I find debatable given the same insulation performance).

Less error-prone in creation - I had written that several times now.

And I had written that with PUR at the beginning of the thread...

Doesn't matter to me now either...