On Feb 1, 10:28 am, The Natural Philosopher wrote:

I'm assuming a DPM is the same speak as a vapour barrier? I'm loath to
do this as it would entail lifting ALL the insulation (Pink Panther +
original).....

No need to lift the original.

Just put a seal between it and the other..

The original will stay warm enough not to condense..

If there's condensation already between the old and the new how will
putting an impervious sheet inbetween solve the problem?