Kitchen/shed extension

FreeBear

grumbler said:

Jeepers_Creepers said:

...with a layer of high-quality polyurethane insulation bonded to it

I'm sorry to be pedantic, but polyurethane foam is soft. It's the one used in furniture.

Celotex is polyisocyanurate foam

To be equally pedantic... Rigid polyurethane foam (PUR) is produced from the same basic chemicals as Polyiscyanate foam (PIR). The main difference is the ratio of chemicals which gives rise to a slightly better fire resistance for PIR.

In terms of insulation value, there is nothing to choose from between the two.

The polyurethane foam used in furniture uses a different catalyst along with a bunch of other chemicals to provide elasticity and fire resistance. It is perhaps a little unfortunate that the term "polyurethane" covers a wide range of materials, all with differing properties.