Extension Slab - Should I be Changing Design

[Tin Soldier]

Hi there

 

I've got 137m2 footprint SIPS Built Extension planned for next year

 

Foundation/Slab design by architect is very much standard fare (after reading this forum) strip fill foundations, 100m Kingspan TF70 insulation, 100mm Slab and 70mm UFH Screed.

 

Is it worth looking into changing this to a more thermally efficient slab? would it require more architects and SE fees, more planning fees? or is this something I can pursue myself and have building control approve?

 

I'm already panicky about my soleplate rotting away to nothing, now I'm having doubts about the foundations/slab