In New Zealand we can get either Celotex GA4000 or Kingspan K10/12 PIR boards.
Looking through the specs for each product, the R value for the GA4100 (100mm) board is 4.50, whereas the R for the K10 (100mm) board is 5.00. The companies quote differing standards for determining the Lambda values (BS EN 12667 for Celotex and BS/IS EN 13166:2008 for Kingspan. Do the different test methods yield different results?

In short, is there an actual difference in the thermal performance for the same thickness?
Both products are about the same price per sq metre.

Thanks

I understood only the (in my experience much more expensive) 'Kooltherm' products were phenolic. The bog-standard K'span I understand to be Pu-based.

**Edit: Silly me. Oops, the K10 *is* the Kooltherm. I should have checked first.

In that case I am somewhere between surprised and amazed that it's the same price as Celotex. I was quoted so much more for Kooltherm than for 'standard' K'span/Celotex (for only a gnat's whisker's better lambda) that, if space is available, it has always been cheaper to use the basic Pu board and go up 25mm.