Our winters are long and sometimes cold. I think all beekeepers think their winters are the worst ever. We can get -40C but 2012-2013 has been mild. Winter snow can be from the start of Nov. till the start of May. There is a book from our area, Gardening Between The Frosts, that claims we only have a 60-70 day growing season, but I think we are slightly better than that. I would say we are similar to and the same Lat. as Edmonton, but we can get lots of rain as well which can be hard for everyone in the summer.
We winter and run almost all our colonies in single hive bodies. There are several reasons for this and we would like to credit the Pedersen‘s of Cut Knife, Sas., for their info regarding this system.
Most beekeepers, especially in the North, know that bees love the warmth. They want their nest to be as warm as possible here all year long. It is rare for us to get very hot weather, so at all times of the year it is easier for the bees to maintain the proper temperature of a smaller cavity. I found that with doubles, the bees moved up right away come fall into the upper box and then they left the bottom empty and cold and collecting with dead bees. In the summer I tried running my hives with unlimited brood nests but then the bees created a long narrow nest and did not use 2 or more combs on the sides of the boxes.
I have tried several insulating materials and have now moved to using blue/pink styrofoam. It is easier to stack when not in use, has better insulating qualities, does not absorb water, easier to make entrances, easier to attach to the hives and is harder for mice to get into. It is more expensive. I am using 2″ on the top and 1 1/2″ on the sides, I have yet to move to using it on the bottoms but will probably in the future. Right now I do close off screened bottoms and entrances, and have some reflective bubble that i put under. It is nice and easy to clean. I like to pack them 4 to a pallet, screw the insulation to the hive, cut holes for upper entrances and then wrap black plastic over top.
As mentioned, we are now also feeding in the early fall.