winterization - remove the screened bottom board or not?

[woodchopper]

It'll more than likely boil down to what breed of bees you have and their health going into winter on whether they'll survive.

Because our surviving colonies are all from Wilbanks I'm willing to bet it all depends on the second part of your sentence and not what breed they are.
What part of So. NH are you from? We have hives just outside of Rochester, NH.

[Bee-Mover]

Well I am trying something this year as I did have moisture issues last year.  I am leaving the bottom open. 

First, the hives are elevated 8" off the ground to allow for air circulation in summer.  But this winter what I did was make a box out of 1" foam board that slides loosely over the outside of the hive, leaving the exit area open, but all the way from the ground to the telescoping top other than the bottom opening insulated.  I note this year the bees are flying at 40 degrees, whereas last year 50 was pretty much the magic number.

Again, this is an experiment, I went into winter with two strong, one moderate and one weak hive.  Spring will tell me how it worked. 

Would you please post a picture of the foam board jacket you've mentioned?  I'm planning to do the same for mine, and I've love to be able to see what you did.

[Steel Tiger]

Because our surviving colonies are all from Wilbanks I'm willing to bet it all depends on the second part of your sentence and not what breed they are.
What part of So. NH are you from? We have hives just outside of Rochester, NH.

A local beekeeper sells Italian packaged bees that are shipped from Ga. Not saying that they couldn't survive our winters, they're simply not bred to survive.
I went with northern raise crossbreds from Vt. I'm building more hives and hoping to make some splits in spring and do some trades for other northern surviving stock.
I live just south of Manchester. I go to Dover quite often.