On Tuesday, 14 June 2016 11:04:22 UTC+1, 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?
--
Tim Lamb

Only a couple of inches makes a big difference in a doorway hieght usagewise.
Is there a damp proof membrane under the floor already?
If not, it needs to be taken up and remedied along with insulation.
Lot of work.