VCL under rafters

[concretedan]

Hoping for a bit of advice if possible..

I am about to place insulation (40mm celotex) under my rafters in a new flat roof and then fix foil backed plasterboard under this. Do I still need a VCL stapled or fixed between the insulation and plasterboard?

Thanks in advance

Dan

 

[freddiemercurystwin]

No the foil on the back of the PB works as the VCL. Assume you're venting the gap above the insulation. You realise 40mm Celotex is pretty thin let alone complies with anything!

 

[concretedan]

Thanks for the quick answer. I'll have about a 75mm ventilation gap above the 100mm celotex between the rafters with 40mm fixed under the rafters. This was specified by my BCO. It's slightly less than I'd planned as I over compensated for my P/R and cavity, which is no bad thing I suppose.

Cheers again,

Dan