JCK

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

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!