"Andrew Gabriel" wrote in message
...

I've done this with 10mm copper, and it seems to be working well.

I know someone who did something similar. He used 8mm copper coiled pipe. He
clipped it to the side of the joists, about 1/4 way down, all along the
length of each joist in one continuous loop. He use two loops to even out
the heat - hottest in the centre of the room. The pipe did not touch the
joists, running though joists through 3/4" holes.

The control was a simple room stat and zone valve. The boiler was set to
65-70C. He did not lay the floor covering until one month after in case of
floor shrinkage. It works OKish. The on-off control does not make matters
better with temperature overshoots. The floor is warmish, but lots of
insulation beneath the pipes in the floorspace.

His boiler is old and he plans to fit a condensing boiler I suggested a
Broag dual temperature boiler using a 3-way valve DHW priority system,
This, runs the boiler temp to maximum when heating DHW. He plans to put UFH
in a similar way under all his suspended ground floor. I told him to put
larger rads upstairs and run the lot on the weather compensator, with 55c
max temp on the compensator slope.