Placing the AVCL in between insulation layers

[David Cooke]

Hi,
This is a hypothetical design stage build up. I have the AVCL applied onto OSB on the warm side of the PIR layer but on the cold(er) side of the mineral wool. It seems to get the all clear from Ubakus with regards to condensation risk, but sandwiching like this hasn't gone down well with the big insulation manufacturers I've approached, or my usual building control officer.
I'm OK with moving the AVCL inboard of the mineral wool in order to satisfy building control/warranty checks but am wondering why the difference of opinion?
Am I using UBAKUS correctly (I use it rarely)?

If I am, could I present the UBAKUS output to the BCO to support this method?

Am I missing something that the big insulation manufacturers are aware of?

 

Thank you for your thoughts!

David

 

Roof_1.pdf

[David Cooke]