ᐅ Foam glass gravel: yes or no?

Not for that, SirSydom... I believe you don’t have to go along with every nonsense, even if I can’t scientifically prove this nonsense (just a note before someone comes back at me with missing evidence). Sometimes, in my opinion, simple common sense is enough.

Best regards, Bauexperte

Insulating against the soil makes sense—at least on the sides. In my opinion, insulating under the slab is pointless, and I agree with the construction expert regarding the load-bearing pressure; I simply don’t trust it based on my gut feeling.

According to the Energy Saving Ordinance calculation, a certain amount of heat flow already passes through the floor slab. Moreover, there are only 12cm (5 inches) of EPS insulation between the warmest spot in the house—the underfloor heating pipes—and the cold floor slab. Between the domestic hot water circulation and the floor slab, there is even less insulation.
I was having doubts because, mathematically, that already represents a considerable heat flow.

But if you practitioners say so…

I think you are correct regarding the pipes, but a distinction must be made between houses with and without a basement (usually, there are few or no pipes on the basement floor slab, but more on the ground floor slab).

From a calculation standpoint, we solved this with PUR to avoid compromising the floor construction – whether 12cm EPS (5 inches) will be sufficient will have to be determined by the thermal insulation calculation.

I would have really preferred to use foam glass gravel (FGG) as perimeter insulation and to avoid all that Styrofoam stuff. From what I’ve read and heard about FGG, it sounds brilliant in my opinion. However, our planner reacted like most people here: kind of like, “Oh no, we’ve never done that before. Where are we supposed to staple the underfloor heating pipes then?” Actually, there’s quite a lot of information available online. I also saw prices from the manufacturer "Veriso" (per cubic meter; you then have to calculate the price per square meter depending on the thickness, plus VAT). Of course, it’s more expensive—that’s the only downside.
Best regards, Steffi33.

PS. Exterior walls are best insulated from the outside rather than the inside. I imagine it’s similar with the floor slab—better to insulate directly under the slab than on top of it (but that’s just my gut feeling).

For our bungalow, the slab will be built on strip foundations. The energy efficiency consultant recommended insulation both below and above the slab. But how should the foundations be handled then? They are not insulated. Does that even make sense?