On Feb 29, 11:04*am, sm_jamieson wrote:
On 29 Feb, 10:42, John Nagelson
wrote:

It would be more usual to use celotex/kingspan, which is a
better insulator than polystyrene (but more expensive also).
Taped with foil tape to give a vapour barrier.
Simon

Thanks - I will have a look at this. Seems to have very high
resistivity. I've seen it with foil both sides. I guess this is for
manufacturing reasons?

John