Bryan,
it all depends...
I have always used open mesh floors; therefore it makes sense to me to insulate the roof to stop condensation developing. This keeps the hive reasonably comfortable as heat rises so the bees will cluster near the top of the hive, no draughts and the stale air will be exchanged at the bottom.
Before open floors there were various methods of overwintering hives - one which is still used is to put matchsticks under the corners of the crown board in November so the bees cannot propolise up the gaps. This would allow air to flow through the entrance and out of the top.
Interestingly Brother Adam did tests comparing WBC's and single walled hives many years ago and concluded that bees in WBC's overwintered WORSE than in a single walled hive. Recent studies indicate, I recall, that colder winter bees work better in the Spring than ones that have been mollycoddled over winter. (Not sure if the cold bees live longer of if they have more get-up-and-go generally). Someone might be able to remember ..