Anyone who has tried to over-winter chickens in Manitoba (north of 50), knows that it is a delicate balance to achieve. The balance of daylight, warmth, water supply and feed needs to be just right if you want to continue to enjoy fresh eggs throughout the long, cold winter.
We've been keeping our hens over the winter for almost a decade now and have made every mistake you can think of. Trial and error along with research and study have resulted in eventual success for both our hens and our breakfast table!
While our hens are outside from March to November, they just can't withstand the bitter cold and prairie winds that come with a Manitoban winter. Temperatures drop to below -30C, even lower with the windchill (-41C this morning), thus even the hardiest breeds need shelter, food and unfrozen water.
After years of trying a number of different shelters, some which worked and others that did not, we built a lean to addition on our barn to house our hens. While the walls are insulated, the space is not heated with the exception of two regular light bulbs and the hens themselves. Against most conventional wisdom, we do not clean our coop through the winter but add straw, lime, evergreen boughs and leaves throughout the winter forming a layered composting floor which produces a natural warmth for the hens. The coop is warm enough that the water remains unfrozen even on the coldest days and in fact steam escapes when you open the door and you are quite comfortable without gloves and in a light jacket. For water we use fill a large poly tank attached to a line of nipple waterers. We don't have running water in the barn (a someday maybe dream!) so we haul water once a week.
We have both a screen door and a solid door on the coop to allow us to regulate the temperature as the weather changes. A single southern window lets natural light in to the coop. We currently use a mixture of ISA-Browns and Columbian Rock chickens but are planning to experiment with some other breeds this spring.
Our birds tend to drop in production for a few weeks following the move inside (and outside) but otherwise they seem to do pretty well in this environment.... it's almost as if we finally know what we are doing!
Spring time is always a bit of a juggle... we always seem to be moving things around! 
