In message , John
Rumm writes
On 14/06/2016 19:54, dennis@home wrote:
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

Building regs approved doc part L1B (conservation of fuel etc), has the
following to say on floors:

"The cost-effectiveness of floor insulation is complicated by the
impact of the size and shape of the floor (Perimeter/Area ratio). In
many cases existing uninsulated floor U-values are already relatively
low when compared with wall and roof U-values. Where the existing floor
U-value is greater than 0.70W/m2-K, then the addition of insulation is
likely to be cost-effective. Analysis shows that the cost-benefit curve
for the thickness of added insulation is very flat, and so a target
U-value of 0.25W/m2-K is appropriate subject to other technical
constraints (adjoining floor levels, etc.)"

Having UFH pushes the U value threshold down some from the 0.7 mentioned.

I have not tried it, but the following might suit Tim's needs:

http://www.kingspaninsulation.co.uk/...alculator.aspx

I found that. There is no ability to insert less than 60mm of insulation
in the calculation and Kingspan want to e-mail the result.

I guess they might be worth a phone call anyway.


--
Tim Lamb