Hi there,   I've a 125m2 extension being erected next year with a pretty basic floor slab planned.   Floor covering 65mm Screed UFH Pipwork 150mm PIR insulation 100mm c35 concrete with mesh   Whilst looking at the overall prices of each piece of work there's a couple of questions that have come up would it beneficial to change the floor structure to incorporate circa 250mm of eps insulation under the concrete slab, instead of the 150mm pir a