On Jul 16, 4:48*am, Fred wrote:
Hi,

Would I be right to think that celotex, kingspan, and xtratherm are
all pretty much the same and 50mm of one is as good as 50mm of
another, or is one better than the other?

Daft question #2: if attaching to an exterior wall to add insulation,
should the foil side face the exterior wall or the inside of the room?

TIA

Polyisocyanurate has the highest R value pf 7.2" initialy, it is rated
here at R6.7 or so as it looses some R value as it cures, its the
product that is foil faced here in the US. Polystyrene is about
R5"-5.5", and the white foamboard R 4-4.5" With the added value of a
foil radiant barrier Polyisocyanurate is the best beal. Liqued foams
are the same, they vary depending on type from R4 - R 7 per inch