Insulating intersection of flat roof and vaulted ceiling.

[If in doubt...]

If the gap is big enough.,

I was thinking tile vents like this (loads of different options out there):

Clay in-line tile vent | Marley

Product images and information for Clay in-line tile vent

www.marley.co.uk

Yep, they look good and are simple for me to fit

So just on to plasterboard - for the vaulted roof and rear wall section as they effectively back on to cold areas is vapour-check plasterboard recommended / required?. I'm using foil backed PIR insulation already but don't want any issues. If vapour check is needed I see its twice the price of std PB - I do have a stack of 1000 gauge DPM left over, can that be stapled up to the PIR instead of vapour-check?

 

[robinbanks]

Why does that triangle of empty space need ventilating?

 

[If in doubt...]

Why does that triangle of empty space need ventilating?

By vaulting the ceiling in that area an enclosed "Cold Roof" system is made, moist air moving from the warm room space below can form condensation when it gets to cold surfaces, ljke the upper roof section in that photo. There needs to be air movement to get rid of that condensation.