P.S. From the Canadian Association of Professional Apiculturists:
The best way to vent extra moisture from wintering colonies
is with an upper entrance. This entrance is VERY IMPORTANT!
A study from northern Alberta, for example, demonstrated that
either a 1 x 1.5 cm top entrance built into the inner cover or a 2.5
cm diameter hole in drilled into the middle of the upper brood box
greatly increased colony strength, health and decreased the
consumption of honey stores