Plaster board faced insulation - making good?

[Rockingit]

Hi Simon. I'm not particularly worried about these things happening.

It won't cause moisture to build up in the insulation or roof void. For that to happen you need 2 things: A defective or non existent vapour barrier on the warm side of the insulation, and a vapour barrier/total lack of ventilation on the cold side. I have only ever come across such a situation once, a barn conversion where the builder had used DPM as the roofing underfelt, and left no ventilation at all. The small loft above the vaulted ceiling was damp due to the condensation that would form up there. Any sort of ventilation, or breathable membrane, as should be in place such a roof structure, will prevent that from happening.

It will, however create a cold spot on the ceiling, and so there is a small possibility of mould forming there. I think the risk is low - it tends to happen in moist areas of poorly ventilated houses, which this isn't. A solution is to use insulation coverable downlights, and backfill any void created with rockwool, eliminating the cold spot.

My first thoughts aren't about the repair job afterwards, it's wondering if there's physically enough depth available to fit them - I'd drill a very careful pilot hole first and see how far in a rod goes - as often I've seen builders just jam in celotex to whatever the joist depth is for maximum thermal values and then board over it. Also gives you a potential headache with thermal values for your cables, too.

 

[Pretty Mouth]

Update:

The PIR insulation was only between the rafters, not across the face of them, and wasn't bonded to the plasterboard. After cutting the circular holes, I was able to reach in and pull chunks out of the insulation until there was enough room for the downlights, and was also able to rod the cables in the void behind. So no making good required, an easy job.