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The Black moisture barrier paper will not affect the operation of the heater, it is to stop any ingress of damp, and is advisable to have it replaced its is there for a reason and needs to be replaced! once panel is removed you need someone with the necessary equipment to test for damp/rot that may be a contractor , Carpenter, or even your local building control or your insurance company , don't let them just replace the panel all that is doing is covering up the problem it will need proper professional investigation , Damp/Rot doesn't go away it gets worse, its one of the problems with timber structures, and needs to be addressed ASAP.
I would use the second one, as you are a Timber frame building, you need to keep the heat in as well as keeping the moisture out, the reflective foil is ok if radiator is mounted on a outside wall, but then it depends on the level of insulation in the building, and from your past posts it doesn't sound if it is very good.
Reply to the thread, titled "Radiator emitting strong odor when heat goes up" which is posted in UK Plumbers Forums on Plumbers Forums.
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