On 14/06/2016 11:04, Tim Lamb wrote:
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?

Nowhere near what is lost through the roof and walls before insulation.
I would guess at less than 10% before any insulation for a solid floor.
With 25mm of insulation that will take it down to about 2% another 25mm
will take it down to about 1%. Unless the insulation is really cheap and
labour free it will never pay for itself.