DIYbanter - View Single Post

Tim Lamb[_2_]

In message . com,
lid writes
On 14/06/2016 18:44, Tim Lamb wrote:

Come on chaps! Keep it clean...

You have no chance TNP has lost it.

But we are not discussing Brexit:-)

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)?

I was considering removing it to avoid chopping bits off doors. The JG
Speedfit slabs will have about 10mm of PIR foam between the pipes and
concrete slab.

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

Hmmm... cost a bit to replace the Jablite though.

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

PIR for new fit. The pipes clip to the surface.

--
Tim Lamb