I have just been using an aerospace type blanket for insulating ceilings. It is a rather expensive roll of aluminium and that stuff they use in duvets. 8 sheets of ally in the sandwich. The outer sheets are heavy duty, woven with some sort of carbon wire and is a bugger to cut.*
You staple it to the ceiling joists and counter batten the ceiling. It replaces a thick layer of rock-wool. I can't imagine how it will replace that though as it took two of us all day to do two rooms. Mind you that was our first job with this (to us) new medium, on a new site.
How long does it take to lay a load of insulation in an attic? Thinking about that, why not lay the blanket up there? Perhaps I aught to ask that of the site agent.
The counter battens took a pair of nails each joist too, as using one per joist allowed movement in them.
I bet the houses will be murder for WiFi and HAM radio, it's already in a dead zone for phone signals. (They have Cellotex on the walls too. Perhaps they are going to be safe houses for people fleeing the UnitedStatesandAmerica. No screens on the windows yet though.)
*We ended up unrolling it on the floor and cutting it on a plank to save the blade, as they must be as sharp as possible.Measure the required length.
Knock a couple of nails into the plank to act as stops for a batten. Place the plank on the mark and lay the sheet from the wall to the plank. Place the batten on top to hold the sheet tight and cut a few times.
The wadding is like that stuff in chainsaw safety wear, so it drags out with the blade rather than getting cut through. The batten is needed for holding the fabric tight as much as for guiding the knife.