Wintering is location dependent. Even locations along the same latitude will need different methods.. In Maine we NEVER had the winds that we have out here on the Prarie.. Maine gets slightly colder, but without the constant 20 mph winds... SO keep that in mind when you are trying to decide what you should do!!
Here in SE Iowa, temps get to -20.. Usually not for more than a couple of weeks, but I have seen 5 weeks of -20 just as often as I have seen it 65 in mid January horseback riding with my wife...
I winter with a top opening rather than just ventilation, and here is why;
I clean the entrances, and a day later the snow has blown back over them. WITH the top entrance, the bees can still get out if the weather warms up and i dont have to go sweep the entrance every fifteen minutes. These hives sit in front of a group of pine trees to help block some wind, but I have found that the wind whirls around the trees in such a way that it hits the front of the hives.. I may have to rethink where these hives set..
I wrap as Perry has already posted about with expert professionalism, so I wont go there....
Typically most people run their hives with the inner cover notch UP as shown;
For winter, I flip the cover to notch down for the upper entrance/ventilation. I put 2" foam on top of that.. Lay plastic or tape your inner cover hole so the bees dont chew the insulation;
This also raises the telescoping cover to make the upper entrance clear;
Not shown... I also put a 2" spacer under the inner cover. Put newspaper on the frames, leaving about 2" clear to the front of the hives, and pour granulated sugar on the paper, giving it a light misting with water as I pour to make it clump.. Then the inner cover/foam/telescoping cover.
I have gotten quite a bit of Flack for doing this.. but understand. I may NOT get another chance to get into the hives before early March, so it gives me PEACE of mind when the howling winds and temps dont let up before then. I have also found that the sugar absorbs excess moisture and keep sthe cluster dry. Sometimes I open the hive to find the bees have been into the sugar hard, Others have not touched it.. If they do not use it, it lends itself well to making spring syrup, so it is not wasted.
I have heard that the bees make a MESS of it when done this way... This has not been my experience unless it is put on too soon, or left on too late. This is also true of the bees building BURR comb in the spaced area for the sugar.. If removed in a timely fashion they will not build ANY Burr comb, nor make a mess of the sugar...
I have heard of, and seen problems with the newspaper being SOAKED and the sugar falling through... If the ventilation in the hive is adequate, this will not happen. Always make sure the newspaper does not extend outside the hive.. if it does, and it rains, it WILL wick moisture inside. Done properly, and managed correctly this has worked WELL for me...
IN THIS AREA... It may not work for you at all! YOU have to be the judge of your climate and weather conditions!
Screened bottom board?
Not a chance where I live if you intend to leave them open. I know beeks who use them and have argued with me that their bees do fine!!! Upon investigation.. their hives are MUCH better sheltered than mine are. The whistling winds would strip any heat from a cluster in moments.. Using a board in them I may be able to use them with no problems.. I have not tried it so cannot make the judgement.
Cleaning away the snow reveals a handful of dead bees.. This amount doesn't worry me.. its when you cant see in the lower entrance because of the bodies that the fear level increases!!!
Wintering bees terrifies me. I UNDERSTAND what they do, but for the life of me I cant get it through my head that anything cold blooded could survive out there with the temps and winds we have...
Hang on beees!!!!!!!!
Hopefully others will chime in from different climates and post how they manage to pull their bees through the cold months!!