vapour control layer

[ey143]

Does a VPC layer include the silver foil sides of a kingspan / celotex insulation board?

 

[John D v2.0]

Yes, although you should tape it to avoid anything blowing through at the joints

 

[ey143]

huh? if the boards are touching side by side, how can anything blow through it, there's no gap?

 

[John D v2.0]

Shrinkage, movement, site cut edges, imperfect alignment, small items stuck between, warping, etc

 

[tony1851]

If the joints aren't taped, water vapour will find its' way in through the gaps (even if they are very small) because water vapour is very penetrative.