On 20/05/2019 16:38, R D S wrote:
I want to overboard a draughty, uneven floor.

And as I could do with raising it about an inch I was thinking about a
thick insulation inbetween.

Then I started thinking about UFH and there are pre-grooved polystyrene
panels that would be ideal.

So just wondering if anyone has any experience of DIY UFH or any
opinions of UFH in general.

The system we have in the conservatory is embedded in the screed, but
could have been used as you mention.

Our add-on system runs off the normal central heating, via a motorised
valve and unvalved return (like a radiator), but that is far too hot, so
there is a blending valve and a separate pump.

Water is circulated by the dedicated pump, from the floor, through the
blending valve and back to the floor. If the water is too cool, the
blending valve mixes it with some from the main central heating and the
excess naturally exits to the main system.

It works well, but there is about 4" of screed, so warm-up and cool down
are slow. You need to have the heating on well before you need the room
and off well before you finish using it.

Cats love it though!

SteveW