You are reading a single comment by @hoefla and its replies.
Click here to read the full conversation.
-
It's part of the job of the foil on the insulation, so let it do that, and then tape up any gaps with foil tape. You want to stop humid air getting to the cold zone, so gaps between the insulation boards and also gaps around the edges of the ceiling to wall. If you buy separate vapour barrier it's usually a thinnish polythene or foil-backed sheet.
hoefla
Thanks for the information. Realistically I'm not going to get to this now I don't expect, but if I did, what would a suitable vapour barrier underneath the MDF be? Something breathable or just plastic sheet?