>>Wyoming has a dry, cold, windy climate.

Topbarbuy, this is probably the reason why upper enterences arnt as
important in your wintering situation.  I went to your site, and I have to
say I enjoyed it.  I found your observations on the bees using
condensed water on the plexi glass inner cover interesting.
Anyway, we have simular winters in Manitoba Canada, in terms of the
cold, but we have alot more snow and a bit of a longer winter than you
usually get.  This year for example, the snow and wind has fill most of
my beeyards with snow, right to the top enterences.  Some completely
covered over.  Not too worried about it though, not like they are under a
twelve foot hard snow bank.  Most of the covered hives had thawed a
air vent out into the snow drift.
Top enterences provide me with the insurance to be able to overwinter
my bees outside here in Manitoban winters.  With only a bottom
enterence, covered with snow , which stops all ventalation, all the
water vapour created inside the hive cavity by the would simply
condence and freeze in the top box.  Creating a very deadly situation....
Anyway,snow is a wintering situation I have to deal with, and if you can
manage it, it turns to be a great protector from the harsh extreems
from old man winter...
For all you out there, dont dissmiss upperenterences until you have a
good handle on what conditions you actually have to deal with in your
wintering climate
Ian

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