>>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 :::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: -- Visit www.honeybeeworld.com/BEE-L for rules, FAQ and other info --- ::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::