Which celotex boards for extension?

[knuckles]

Hello all,
I am changing my existing conservatory which has a polycarbonate roof to having a slate roof with velux windows with velux vrtical element in the walls. Looking at the celotex website there are so many products, I can't decide which one is best.
I'd like to slate the roof with Redland Cambrian low pitch slate or similar and insulate between and below the rafters and have a vaulted ceiling.
Is the FR5000 board the better performer, I'd like to keep the rafters as slim as possible as there is a constraint on the overall height. The span is 2200mm and I'm looking for a ventilated space 0f 50mm above the insulation.
Basically, what's going to please the BCO?
Many thanks,
James

 

[simonjay]

Hello all,
I am changing my existing conservatory which has a polycarbonate roof to having a slate roof with velux windows with velux vrtical element in the walls. Looking at the celotex website there are so many products, I can't decide which one is best.
I'd like to slate the roof with Redland Cambrian low pitch slate or similar and insulate between and below the rafters and have a vaulted ceiling.
Is the FR5000 board the better performer, I'd like to keep the rafters as slim as possible as there is a constraint on the overall height. The span is 2200mm and I'm looking for a ventilated space 0f 50mm above the insulation.
Basically, what's going to please the BCO?
Many thanks,
James

There are, as you say, loads of variants with slightly different specifications. However, in my experience, if it has foil both sides and is the correct thickness, the BCO will be happy. The difference in thickness required would minimal.
Simon.