> The Germans and many other Europeans put a sheet of thin clear plastic across the topmost box to prevent the bees from propolizing the lid too badly - they might be a better source of data on the issue, but their winters are fairly mild.

I am in Chicagoland. My inner cover is made of clear plastic foil, a 
sheet of 1/8" Reflectixas a seal and 4" of XPS (R-20?). I yet have to 
see condensation above the bees. In the corners, yes, sometimes. My SBB 
is opened all year around.

This year I *testing it with wooden and poly hives*. All are alive as of 
today. I treated for varroa last using both OAV (8 times, starting in 
spring, once after OAE to check the drop) and OAE( 6 weeks in summer).

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