150mm PIR or 150mm XPS insulation under slab

[SS-ProjectBuild]

Hi,

As the title suggest whats better? I know PIR is way more expensive than XPS but dont really know any other pros/cons?

 

[^woody^]

Its roughly twice as efficient

 

[cdbe]

If you have to dig out and dispose of spoil to make space for it, you'll obviously chose a thinner layer of the more efficient stuff.