Fred wrote:
On Sun, 14 Nov 2010 17:59:01 +0000, John Rumm
wrote:

You can almost ignore the bricks - they are of negligible effect
compared to the insulation!

Perhaps that's the easy way to get a rough figure. Work out how much
heat is lost through 50mm celotex and use that for my calculation. I
guess I also need to work out heat lost through the concrete floor
though?

50mm celotex is practically full spec insulation.

Brick k factor is an average of about 1 W meter, so on 4" brick (100mm)
is about a U value of 10 or so,

Celotex is about .020 k so 50mm is a U value of 1 more or less.

Combined its 1/11 or around 0.9 So adding the celotex reduces heat loss
by about 11 times.

As aginst 10 for the celotex alone.