A regular subject for this time of the year.  Clearly wintering in Alaska 
is very different from that in Florida.  I sspeak only for that part of the
world where winter consists of intermittent periodsof sub-zero weather,
periods of rain and the occasional sunny day when the bees can take a
cleansing flight.  Under these conditions I do not consider top ventilation
to be important providing there is plenty at the  bottom.  
>>>>>I heard recently that hive ventilation is most important and that the
hives
should be properly ventilated even if this means that a strong current of 
air is blowing through them. I was also told that when the Autumn (Fall)
feeding is over, that I should raise the crown boards slightly with match 
sticks to give additional ventilation.>>>>>>
With regard to the above quote, a wooden matchstick is around three thirty
seconds of an inch thick.  This gap all round the top of the hive amounts 
to some six square inches of gap, a considerable  "chimney".  No great harm
if your hives are well sheltered but if exposed to winter gales the bees
will shiver, many will die and food consumption increase.
During September the bees glue down the cover board.  If I leave an
inverted can feeder over the feed hole empty for more than  a day the bees
start to seal all the holes.  Place a piece of hessian or metal mesh over 
the feed hole and it will be quickly seaded with propolis.  It would appear
that the bees are saying "No top ventilation, please."  I prefer top
insulation to ventilation but all my colonies have at least twelve square 
inches of bottom ventilation and they winter well.
When one considers the diversity of advice offered, beekeepers appear to be
happy with a very wide range of conditions, lots of ventilation or a
little, at the top or the bottom or both and the bees come through smiling
whatever method is chosen.      Sid P.