The Natural Philosopher coughed up some electrons that declared:

I've got IIRC a P/A of 0.5, so base U-value of 0.73.

Thats not too bad. Whats teh values for suspended block and beam :-(

Righty ho - best effort so far:

http://www.celotex.co.uk/Other-Resou...lue-Calculator

Solid floor, P/A=0.5, 12mm celotex[1] gives:

Overall U-Value = 0.47
Celotex R-Value = 0.522

So floor base U-value =

1/(1/0.47 - 0.522) = 0.62 which is pleasingly similar to 0.73 to make them
believable.

[1] 12mm PIR is roughly similar to 25mm EPS

OK - ran it again for your beamyblock floor:

U-value final = 0.52
R-value (celotex) = 0.522

So sub-floor (uninsulated) U-value = 1/(1/0.52 - 0.522) = 0.71W/m2K

============================================

So, me with my 25mm EPS:

Total U-value with EPS = 1/(1/0.62 + 1/1.63) = 0.45W/m2K

For UFH: Assuming ground is 5C, tile surface is 27C (maybe that over, water
is 27 return IIRC for EasyPanel)

Watts = 19m2 * 0.45 * (27-5) = 190W loss through slab.

For tile temperature of 22C, ground temp of 10C, loss = 100W

If we consider the whole house running on the same time profile:

95m2 * (22-10) * 0.45 = 510W = 60p of gas for 24 hours in ground losses for
the entire house.

I really don't know how the water temperature will relate to average tile
temp, nor what the effective soil temperatur will get to, hence the wild
guesses. But I think I'm in the right order of magnitude, probably withing
a factor of 2.

If I stuck tiles to teh concrete like I was going to, and they got to 16C,
ground temp 5C, then losses would be about 640W for the whole house.

So UFL + fiddling bit of EPS might be no less "green" than having cold feet.

Apparantly there's an option to request thicker panels. I suppose a pervert
could buy their thin panels and stick 12mm or even 20-ish mm celotex under
them, which would be more like 40mm jablite/EPS, but that's a lot of
composite components bonded and I'm already worried about my tiles falling
off.

Interesting stuff.

You know, if the bloody government was as green as it claimed, they give
away copies of a fully featured U-value calculator and a simple-sister
version so people could make intelligent decisions.

Oh, hang on - they don;t want us to think, do they - might expose their
scamming ways.

Cheers

Tim