Hi everyone , we have just done 2 newbuilds and are soon starting first fix, we have prepared the ground floor in concrete slab for UFH, now just wanted some advice for what type of heating system would be most energy efficiant ,I've been looking at the valiant system boiler with an unvented water cylinder bit pricy but heard it's money well spent,each house is 5 bed with 4 bathrooms ( 3 floors) all advice is most welcome thank you in advance.