On 26/01/2021 08:57, Tim Lamb wrote:
In message , Andy Burns
writes
ARW wrote:

OK so this is a refurb and not a newbuild I am working on.

Is the whole thing anywhere near done yet?

One difficultyÂ* we discovered with a refurb and planned underfloor
heating throughout is adequate insulation over solid floor slab.

The original arrangement with wall hung radiators had 25mm polystyrene
under 22mm chipboard. The new system uses slotted polystyrene slabs with
about... 25mm of insulation below the pipes!

We could have put more under but only by losing ceiling/door height.


Don't worry. According to the ?polyplumb salesman at a
self-build exhibition that I visited many years ago, he
assured me that even though the overlay slotted
insulation panels were only an inch thick, it would
still be cheap to run because 'heat rises'.