@Barcon PIRis basically styrofoam which is foil backed so this is the vapour barrier, when i put between the studs any gaps were sealed with expanding foam and then a foil tape over the top of that. They have even said on the PIR the sides need taping up as well, I didn’t have to do this but did anyway for peace of mind.
Put a dehumidifier in the garage last night and got about 2/3 litres of water and the rest of the house is bone dry compared to normal, so will give a week or so get the radiator in there and see how it fairs.
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View attachment 98469