To Mark Hubbard and fellow beekeepers,

You asked about space at the top of the hive for ventilation and upper
entrance.  In general, an upper entrance is a good idea, as you say, for
ventilation, and to provide access for bees.  Ventilation is particularly
beneficial in a humid climate.

There are some drawbacks to an upper entrance, depending on your climate
and the strength of the hive.

1.  How big are the top openings?  Anything bigger than 3/8 inch by 2
inches is probably more opening than needed.  A great honey flow and a
strong colony could use several upper entrances.

2.  What is your location and climate?  Damp climates seem to benefit from
increased ventilation.  In dry climates, the brood area may not have
sufficient humidity if there is excessive ventilation.  Also, dry cold
windy climates (by cold I mean a week or more of below zero (F) weather)
will benefit from less ventilation in the winter.

3.  What is the strength of your colony?  A strong colony can fight off
wasps and robber bees that may invade through excess openings.  For a weak
to middling colony, restricting the entrances will not hurt the colony, and
will help protect them from invaders.

Cheers,
Kyle