Retrofit UFH and LVT

[JCK]

We are having a kitchen extension ( 30m2 in total) which will have quite a bit of glazing and little wall space for radiators so the builder suggested UFH. He suggested a retrofit system ( poly pipe) to be laid on our existing concrete and LVT base ( which has no insulation). 
We would really like LVT but am a bit concerned about heat output considering the lack of insulation  below and the need for 6mm ply and levelling compound above and whether it will get warm enough. We don’t want to significantly increase the floor height so the other option would be to dig down and use a normal UFH system. 
Does anyone have experience of laying a wet Retrofit UFH system with LVT? Or an idea of cost comparison for digging up the floor?

thanks!

[JohnMo]

UFH will be costly to run as as much or more heat will go downwards.

 

Could you do plinth heater's below the kitchen units and do you have space for any tall thin radiators?

[ProDave]

Why have you built a new extension with NO insulation under the floor?

[JohnMo]

7 minutes ago, ProDave said:

Why have you built a new extension with NO insulation under the floor?

I did wonder how they complied with any sort of building regs, but didn't like to ask.

[JCK]

Fair point! The extension part ( side return to a Victorian terrace) will have insulation but the existing house has none!