Waldemar,
Not only do I totally agree with Lloyd, but here, just 10 miles north of
Washington,
DC, we don't have too much snow much years.  However, we do see temperatures
down to 10° and wind.  I have all my colonies on screened bottom boards for 6
years.
They sit on 12"x16" cinder block. so they are 8 inches off the ground.  I
don't have
any winter losses, but I have STRONGLY preached an upper entrance cut in the
inner
cover for well over 40 years.  Ventilation in the winter is extremely
important
whereas COLD weather, even -40° does NOT kill healthy bees.  Read Dr.
Southwicks
work on confining bees for 30-60 days at temperatures as low as -80°, and over
90% of all the tested colonies survived.

I hope I have helped.

George Imirie, retired scientist
Certified EAS Master Beekeeper
Beginning my 72nd year of beekeeping near Washington, DC

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