underfloor air cavity possible

Exploring the possibility of having underfloor heating upstairs instead of rads in conjunction with the geothermal heating system. It is a dormer done with blocks. In order to pour concrete on it you have to have a precast concrete structure which works out quite expensive.

I was just wondering does anyone have any experience in doing it this way?
see pic here

[broken link removed]

So Just go ahead use the timber flooring - battens and underfloor in between them.

Any help is appreciated.
kildarebuild

Hi Kildarebuild. I have 150mm solid concrete 1st floor + 25mm High Density kingspan + UFH pipes + 90mm screed. Not that expensive - approx 4500E over 100m2. If you use hollowcore concrete you will need to pour the screed directly to the hollowcore with the UFH pipes between - up to a 250mm mass of concrete to be heated - slower reaction - longer to cool down. I've also seen UFH in a screed on timber joists in a neighbours house - joists looked a lot bigger than normal - but possible. Hope this helps

Here is another way of doing it. Put ply on top of your joists on 1st floor. Put Battons on top of the ply (1"3/4 deep). Place these battons at a distance of around 12" apart. Put foil backed insulation between the battons. The foil should be around 1" thick. Now run your underfloor piping on top of the foil insulation. You can get pegs that clamp the pipes onto the insulation. You can now put floor boards on top of the battons and you should find that the underfloor pipes will be just touching the underside of the boards. The foil insulation will reflect all heat upwards. Now you have no screed to heat and so a quicker response time. you also won't need heavy duty joists. The negatives are that screed will kill noise upstairs while the battons won't.