ᐅ Foam glass or high-compressive-strength alternatives for perimeter insulation

Good morning,

In this thread, I already shared how our "building disaster" has unfolded so far. Now we want to move forward again and have therefore removed the facing brickwork from our new build and exposed the base to properly insulate the plinth. (A 12cm (5 inches) perimeter insulation was originally planned.)

Since there is only about 13cm (5 inches) of "support surface" available in front of our slab for insulation and possibly cladding, our architect advised us (but is still checking) to install foam glass insulation up to the screed level. (Because the facing brickwork can then be laid on top thanks to its high compressive strength.)

Since this foam glass is very expensive (and questionable regarding disposal), I would appreciate it if anyone could suggest alternatives for insulating the plinth.

As my information (as a layperson) might be somewhat limited, I am happy to provide more details upon request...

Well, the standard perimeter insulation is made of XPS. Isn’t that an option?

Unfortunately, I am not familiar with the insulation material myself and do not know its compressive strength.

The main argument is that there is only 13 cm (5 inches) of space on the strip foundation, and we were advised to use foam glass due to its high compressive strength, so that the facing brick can be supported by it.

XPS is available in different compressive strength classes, as far as I know, up to 700 kN/m² (14,900 psf). Foamglas offers even higher values, but the question is whether that is really necessary.

Oh wow – this is also beyond the limits of what I can assess (which is, after all, the architect’s responsibility).