It happens that Mary Fisher formulated :
On the contrary - we found that we had MORE condensation on dg windows after
our cavities were insulated - donkey's years ago. The walls were then warmer
than the glass so the condensation appeared on the glass.

It proved that the cavity insulation was working!

Hi Mary...

That was not our experience, though I suppose it depends how much
moisture is absorbed into the cold walls. The DG was installed first
and we initially had similar problems to the OP. I then added
ventilation followed some years later by the CWI.

Our internal atmosphere is now so dry, that we have had to resort to
adding water evaporation trays to the tops of radiators to increase the
humidity in winter.

--

Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk