Insulating floors

[Fizzing]

Hi

I have built a concrete floor in a new extension. It will be insulated with 100mm Celotex and then screeded with 75mm screed.

I haven't decided on the final finish floor tile so unable to work out the thickness that will needed exactly. To be on the safe side, I have allowed ca 65-75mm for final floor finishes after screed to do the following:

1) either use a really thick slab ca 45mm and bed it in sand cement to make up to the 65-75mm

2) or use insulation backed boards to make up the height, then u/f heating and a 12-15mm floor tile to make up the total of 65-75mm

If I go for option 2, it means the screed will be sandwiched between 2 layers of insulation - underneath with Celotex and over with insulation backed boards.

Is there a technical DIS-advantage of doing this? what problems may occur if I did this? (e.g. slow to heat, condensation etc)

Thanks

 

[gasanstuff]

I put the UFH pipework clipped straight on the insulation. Then screed over the top. 65mm poured or 75mm normal screed. Have been advised by a few UFH manufacturers to not go over 90mm depth of screed.

Obviously the thicker the solid mass you are heating the longer it takes to respond.