insulating attic room with kinspan

[striker59]

We have started insulating an attic bedroom.We have taken down the old lath and plaster between joists and are filling in with kingspan. The kingspan we have has foil on one side only and paper on the other. We've started putting it in with the foil to the outside wall and the paper facing into the room but are now wondering if this is the wrong way round- does it matter, and if so can we get round the problem without taking it all out again eg by putting in a polythene membrane before plasterboarding?

[Perry525]

Kingspan is a proprietary version of polystyrene, it has a higher level of insulation at the time it is fitted as the holes in the plastic are full of an inert gas.

The insulation value quoted is based on its expected value at 15 years after some losses.

The aluminium cover is merely a device to prevent the gas leaking out too quickly.