Between-floor insulation

[ab]

I've taken up some of my upstairs floorboards to install pipes, and am wondering whether it's worth putting some insulation under them before I replace them.

Generally I heat the ground floor of my house, but leave most of the first floor unheated. I notice that the upstairs rooms do get quite warm when the heating is on downstairs.

The floor at the moment is Gyproc ceiling + 20cm gap + 18mm chipboard.

I've seen this "Foil Tec" at Screwfix:

?_dyncharset=UTF-8&fh_search=foil+tec£125 seems pretty pricey for a sheet of foil, and unfortunately this is a greater quantity than I'd need. Also I can't see where you can obtain the installation clips mentioned on the manufacturer's website: it's double sided, presumably to stop heat transmission in both directions, but I'd not be too worried about heat heading "downwards" as I rarely heat the upstairs while the downstairs heat is off.

Are there cheaper options available? What do new-build houses use for insulation?

[a]

Sorry I realise this was rather a rambling question. Leaving aside the detail of it all, I'd be interested to know what new-build houses use for insulation above the ground floor ceiling?

ab wrote:

[dom]

Generally it's acoustic rather than thermal insulation.

out "Crown Acoustic Floor Roll"