Help! I have been spreading micafill vermiculite over existing thin fibreglass between the joists in my attic. Having almost finished the job, I happened to read in a Readers Digest DIY manual that to prevent condensation you first need to lay strips of aluminium foil between the joists, then put your insulating material on top of the foil. This advice is not repeated elsewhere so far as I can see. Am I OK to dispense with the foil? At this late stage, installing it under the vermiculite would be a problem.