Will the foil on insulation panels affect the pipework / screed?
The foil on insulation panels will not affect the UFH pipe. The issue is when a liquid flowing screed is used, the foil then reacts with the screed causing air bubbles within the screed. This can be avoided by installing a polythene membrane over the insulation panels. A sand/cement screed will not react with the foil. In both cause the pipework will remain unaffected.