Vapour layer over PIR?

[sgg123]

Hi all,

I am about to board out a cold roofed room. I have 75mm PIR between the rafters and another 75mm layer of PIR under the rafters.

Will the additional layer of PIR on the warm side be sufficient for vapour control - or do I need to still attach a VCL film? If it's the latter, what is the accepted way of attaching this VCL to the PIR?

Thanks

 

[freddiemercurystwin]

If it's a continuous layer of foil backed boards then just tape over the joints with some foil tape. The purpose of the foil on the insulation is to act as the VCL.

 

[SFK]

Agree with above
In my opinion Toolstation does great Foil Tape (it is Aluminium metal)

Aluminium Foil Tape

If you need a high-performance foil tape for jointing insulation boards and lagging, look no further. Ultratape’s aluminium foil tape is perfect for use on foil-faced pipe and slab sections, and is particularly effective at protecting against the effects of dust and moisture.This self-adhesive...

www.toolstation.com

Screwfix does terrible foil tape (it was more sellotape than metal.

Sfk