On 14/06/2016 18:44, Tim Lamb wrote:


Come on chaps! Keep it clean...

You have no chance TNP has lost it.


So the 4" concrete pad in the middle of the cottage is in close contact
with piping at 55C. The pipe temperature will vary due to thermostat
demands but should settle at something above say 10C for the surrounding
ground. Slow thermal response is not a huge concern for 24 hour occupation.

What happened to the 25 mm jabalite (expanded poly)?


Cast concrete 100mm + 25 mm expanded poly has a U value of about 0.6 wm2/k

Cast concrete 100mm has a U value of about 1 wm2/k

Cast concrete 100mm with 50 mm expanded poly has a U value of about 0.4
Wm2/k

So the extra 25mm will save you about 0.2 Wm2/k
While the first 25 mm will save you about twice that.


PIR foam is slightly better with the additional 25mm giving a U value of
about 0.33 Wm2/k


Within the site, I assume there will be a thermal gradient between the
concrete and the subsoil. Is this likely to cause significant losses
other than near the edges?


New work will probably have 4" of insulation under the screed and pipes.

PIR foam would give a U value of about 0.16 Wm2/k.
Expanded poly would be about 0.25Wm2/k