Excellent point Trumpy, it's not just me then! I read somewhere yonks ago that polystyrene foam should not be allowed to come in permanent contact with pvc cable insulation in a building. Some sort of reaction between the plastics causing degradation of the insulation? In my workshop I have 60mm (2 1/2") P.S. foam/10mm sheetrock as the insulation boards and ran a lap of heavy polythene DPC over the cabling and pvc conduit before fixing the plasterwork, poo-pooed by the Scot neighbour as a waste of time.
Alan
