mesh floor in winter

To assist in the control of varoa we placed wire mesh floors on both of the
hives this year with a draw arrangement at the rear of each hive to remove
and inspect hive rubbish.

As in previous years at this we have now closed down the entrance gap on
each hive to prevent intruders.

It is understood that the majority of problems that occur within the hive
during the winter are in fact caused by dampness and not necessarily
coldness. Is this so ?

Should we therfore remove the rear tray to allow ventilation (convection
type) through the hive?

Thanks in avance for your reply
gs