Dennis had a post on his site with a very interesting look at the importance of condensation in the hive. His site no longer seems to be up, but an archived copy of his site is still available.
With American beekeepers in particular, the idea of upper entrances for ventilation is very popular. What Dennis observed while using a water feeder inside a hive by placing a plexiglas cover on top of his hive, seems to go against that practice.
He observed that very little condensation occured during the winter. A good deal of condensation did occur during the spring and fall, but the bees quickly made use of this. His feeling was that this saved them the work of collecting water from outside the hive, and provided a needed water source for his bees when an external source was not necessarily available.
Will his ideas work for you in your climate? I don't know, but I do feel the topic of ventialtion and upper entrances probably deserves a little more thought and consideration than most bee books suggest.