On 14/06/16 13:38, dennis@home wrote:

You really don't understand physics do you!

You might, but you've overlooked one thing - see below:

If you put pipes onto and they are at 55C that will only about double
the heat loss through the floor and that loss is only the 1% so at best
adding another 25 mm will take it to the same level as a normal room
without UFH.

Just for the understanding.. if you double the temperature difference
you double the loss. If you double the insulation you halve the loss.


No - because you've incorrectly assumed the substrate temperature under
the subfloor remains the same (your assumption appearing to be about 0c )


This is true of walls and roofs. But the general mass of earth under the
house will rise in temperature with an increased floor surface
temperature, so it is far from obvious how much difference an extra 25mm
of insulation will make.

I've never understood the details, but I can see enough to know your
argument has an error.