Insulation & vapour check polythene membrane

[Simon_B]

Hi,

We've just had a GRP Flat Roof installed and are now putting in the insulation between the rafters it specifies Celotex 120mm XR4120, it then continues with a void over for vapour check polythene membrane.

Whats is the later part is this a separate item or built into the Celotex, I can't find confirmation either way?

Thanks

 

[bobasd]

your post is confusing.is this a cold roof or a flat roof and position of vapour barier depends on position of insulation. more info or a photo needed

 

[Simon_B]

Hi, it is a cold roof

 

[John D v2.0]

Polythene is a separate thing. 120 won't be enough to meet regs if its between. The void would be above with ventilation. Who designed the roof buildup?

 

[Notch7]

Vapour check is always on the warm side.

Cold roofs are tricky to fit vcl if there are downlighters.