Question about SBB in north

[Dallasbeek]

I'm building a top bar hive with screened bottom board for a nephew in St. Paul, MN.  I can build it with a solid board to fit under the SBB, but wondered about what you folks up north do.  I know humidity is at least as bad as the cold.  I'm following Michael Bush's practice of having a top entrance, but then what about ventilation?  I'd appreciate advice on whether you use the SBB in the winter or close it up tight and about ventilating iit, etc. In Dallas, some of us leave the SBB open because we rarely have very cold temps.
Thanks.
Gary

[Bush_84]

I wintered a tbh in mn once.  I kept bottom sealed up tight. 

[Robo]

Top entrance will allow moisture to leave.  I would not have a top entrance and screened bottom,  the cold will just flow right through.

TBH make it tough on the bees in extreme cold,  don't make it any worse.

[Dallasbeek]

Thanks, Robo and Bus_84.  I'll include a board and clamps to hold it tight against the SBB.  He can drop the board in summer and raise it in winter that way.

Gary