Vaulted ceiling damp patches

You can try packing out round the lights, if that fails an underdraw or insulation below the rafters will sort it.
You wont know till next winter.
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Utimately it looks like you've not got a vapour barrier which is usually foil taped insulation below the rafters usually 25-50mm or you can use foil backed plasterboard.

For now as suggested I'd pack out the voids better with insulation try not to cover the down lights though.

Also the down lights do they have a rubber seal on the backside of the bezel? This usually provides some seal to stop warm moist air from passing the cut outs and condensing.

If the bezel doesn't have this it's worth sourcing something similar.

Again it's probably a problem you won't encounter again now till the cold weather kicks in again.
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Either way, the shaddowing is only appearing in the areas where the down lights have had the insulation cut out, suggesting that whatever insulation type has been used it seems to be working? By the way if I’m going to try packing the area with mineral wool can anyone suggest an actual product? It will need to be soft, flexible type because I only have the 2” down light holes for access.

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