>Hi Jean-Pierre
>Personally I belive it's better to have a bottom board that provides sufficient
>ventilation. There are different constructions on bottomboards that will do the
>job,
 
>I think most of the humidity is produced by the bees themselves in the
>metabolism when they consume the feed.
 Put the effort in finding a bottom construction that is efficient enought.
>
>Are all beekeepers in the US and Canada using top entrance during winter?
>What is the reason for it when it's not needed here? The north of Sweden has
>as cold winters as Canada, and probably longer (lat 65).
 
I don't think the length of winter is the problem. Take our area, in the
last 48hrs we have had 4ft (thats 1 !/2 metre of snow) My hives would be
almost buried, the wind around them keeps them in a small depression.
Without a top entrance the bees would be in trouble, as today it is fairly
warm and brilliant sunshine. I have found that when the bees are resticted
ie.no exit, they become very agitated, and the moment an exit is made they
come flooding out.
        The bottom board you have described is a variation on a theme. I
have seen them made of slatted wood, which also works. One problem is mice.
As you can't see under the hives to watch for damage. Plus I firmly believe
there should be air exchange, to remove moisture and CO2, needs a top
entrance. My original thread on suffocation.
        During my experiments my winter lose has gone down to Zero, which I
think speaks volumes.
        I have been experimenting for the last 5 or 6 years with ventilation
and have come to a series of conclusions.
        Ventilation is a year round necessity.(helps to keep the hive dry)
        Top entrances (top ventilation) are essential.
        The best packing for bees is more bees. A big hive in the fall,
comes out          bigger in the spring.
        A well ventilated hive, by comparison is larger.
Most beekeepers have 2 opinions the first is "They are right" the second
"Everybody else is wrong"
        Finally if you put 10 beekeepers in a room, you'll get 12 ways of
doing the same thing, each one will work.It would appear you take the choice
that works for you!!!!
 
 
 
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