Underfloor heating.
Insulation thoughts... the existing ground floor has 25mm Jablite topped with 22mm chip. Recommendation is to over fit 25mm of pre-grooved insulation and a further set of flooring: chip + Vinyl or engineered hardwood.
Downside is loss of height in doorways.
What is the real energy loss in heating a relatively uninsulated floor slab in a roughly square building? For 24 hour occupation, doesn't it come down to what is lost at the edges?